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Building and Environment 106 (2016) 205e218

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Building and Environment

journal homepage: www.elsevier .com/locate/bui ldenv

Evaluation of passive ventilation provision in domestic housingretrofit

Oliver Kinnane a, *, Derek Sinnott b, William J.N. Turner c

a Architecture at Queens University Belfast, Irelandb Department of the Built Environment, Waterford Institute of Technology, Irelandc Energy Institute/Electricity Research Centre, UCD School of Electrical and Electronic Engineering, University College Dublin, Ireland

a r t i c l e i n f o

Article history:Received 27 April 2016Received in revised form24 June 2016Accepted 25 June 2016Available online 27 June 2016

Keywords:Passive ventilationRetrofitBackground ventilatorsEnergy efficiencyIAQBuilding envelopePart F

* Corresponding author.E-mail address: o.kinnane@qub.ac.uk (O. Kinnane)

http://dx.doi.org/10.1016/j.buildenv.2016.06.0320360-1323/© 2016 Elsevier Ltd. All rights reserved.

a b s t r a c t

Increasing energy efficiency in the residential sector, while maintaining adequate home ventilation forhealth and well-being, is proving to be a challenge. This study assesses the efficacy of passive ventilationstrategies designed to comply with building regulations and imposed after housing energy-efficiencyretrofits. In particular, it focuses on the provision of ventilation using background through-wall vents,which remains a common strategy in a number of European countries including Ireland and the UK,where vent sizes, related to floor area, are stipulated in building regulations. A collective of socialhousing, with background through-wall vents installed post thermal retrofit, is taken as a case study.These homes are modelled to interrogate the impact of the passive ventilation strategy on house airexchange rate and thermal heating energy loads. The reaction of occupants to through-wall ventinstallation is decidedly negative and many block vents to limit thermal discomfort and heat loss.Simulation studies show significant external air ingress through vents. A wide range of effective airchange rates are observed when vents are sized without reference to building airtightness, and signif-icant energy penalties result for the leakier homes. This study evaluates the provision of passive through-wall ventilation as part of a retrofit programme and shows it to have a number of drawbacks that mayimpact on the health of the building and its occupants and ultimately be at odds with the aims ofachieving energy efficiency in the residential sector.

© 2016 Elsevier Ltd. All rights reserved.

1. Introduction

Retrofit of the current housing stock is essential as we aim toprogress towards energy efficiency and mitigate climate change. Itis also essential to improve the living conditions of the many wholive in substandard conditions. Housing in Ireland and the UK issimilarly constructed and accounts for 1.65-million and 26-millionhomes respectively. Both countries are undergoing a suppressedrate of new build, and significant retrofit of the existing stock willbe required to achieve ambitious energy and carbon reductiontargets [1]. The housing stock in Ireland is some of the most ther-mally inefficient in Europe [2], with significantly substandardproportions and high cases of thermal discomfort and fuel poverty[3]. However, good progress has been made recently to improvehousing and reduce the associated thermal energy load [4].

.

Similarly in the UK, savings made through insulation and heatingefficiency since 1970 are estimated to have halved the possibleenergy consumption related to housing [5]. Significant energysaving is available through housing retrofit, however it is impera-tive that retrofit interventions made to improve thermal perfor-mance do not detrimentally impact indoor air quality, and therebythe health and well-being of occupants.

In North-Atlantic climes people can spend up to 90% of theirtime indoors (either at home, work or commuting) [6]. Ventilationprovides fresh air to dilute or displace stale indoor air, and is longrecognised as key to enabling good indoor air quality (IAQ), andoccupant comfort [7]. The provision of indoor air of high quality isimportant for good health [8], and is a right of all people [9]. His-torically, uncontrolled infiltration has served the needs of homes inmaritime-temperate climates such as Ireland and the UK. However,contemporary buildings are increasingly airtight, and purpose-provided ventilation is required to provide controlled air changeand reduce condensation risks etc. Airtight housing is increasinglybeing related to lung diseases including growing incidences of

Nomenclature

Afloor floor area (m2)AL effective leakage area (m2)ACH building air change rate (/h)ACHeff effective ventilation rate (/h)Q50 building airflow rate at 50 Pa (m3/h.m2)Qt target ventilation rate (l/s) and (/h)te turnover time (h)te time-averaged turnover timet time (h)

1 The equivalent area is defined in the 2009 version of Part F as thus: ‘The area of asingle sharp-edged hole that passes the same air volume flow rate at the same applied

O. Kinnane et al. / Building and Environment 106 (2016) 205e218206

asthma [10] and risks of radon-related lung cancer [11]. Thermalretrofit can also result in an unintended increase in airtightness[12]. A preceding study to the work presented here reported a 20%reduction in infiltration following insulation installation andassociated remedial work [13].

Considering the increased association between airtight, energyefficient homes and dangers to occupant health, provision ofreliably-sufficient ventilation is critical for the maintenance of goodIAQ. This necessity is addressed by the building regulations thatstipulate varied ventilation rates in rooms depending on theirfunction and associated risk of moisture and pollutant generation.A variety of means of ventilation provision are proposed in Tech-nical Guidance Documents (Part F) of Irish [14] and UK [15] regu-lations. These include strategies based on passive, cross and stackventilation; mechanical extract and mechanical heat recoveryventilation (MEV and MHRV respectively). Passive ventilation,provided by through-wall background ventilators, remains themost common ventilation strategy in new build and post retrofitdue to low cost and ease of installation. However, these uncon-trolled vents can result in cold air ingress during winter andshoulder seasons. They are therefore poorly perceived by occupantsand often blamed for thermal discomfort and unwanted noise [13].Compensatory high heating loads can also result. Air exchange,including infiltration, exfiltration [16] and designed ventilation [17][18], is a primary contributor to building energy loads, and isbecoming proportionally more significant as conductive heat lossesdecrease with better insulation standards. The aims of residentialenergy efficiency, and the provision of adequate ventilation, areproving difficult to reconcile.

Research literature abounds with policy review [19] [20] andtechnical assessment of thermal retrofit intervention [21]. There isalso a significant amount of work focused on mechanical and, to alesser degree, hybrid ventilation systems [16,22e24]. In contrastthere is a paucity of literature focused on the most common meansof home ventilation provision, with only a few studies evaluatingpassive ventilation [25] [26]. This study attempts to redress thatshortcoming by examining case-study social housing pre- and post-retrofit for IAQ and energy impacts. Modelled scenarios are pre-sented that display the significant impact of background ventilatorinstallation on these small homes with varying envelope airtightness levels. Air change levels in these example homes arecompared with regulatory levels across different European coun-tries. A significant energy penalty is shown to arise from passivebackground ventilation, augmenting cold air ingress in homes withhigh infiltration. Varying energy consumption in the case studyhomes results from occupants taking drastic measures to limit thenegative impacts of the designed, background ventilation strategy.

Building on the work of Sinnott [13], this study examines asample of Irish social housing. Terraced and semi-detached e the

most common dwelling types in Ireland (45%) [4] e are investi-gated onsite and then modelled to examine the impact of thepassive ventilation strategy on house air exchange and heatingenergy loads. While social housing is used as a case study, the re-sults of this paper can be extrapolated to a much larger group ofdomestic buildings.

2. Background

2.1. Housing stock retrofit in Ireland

Retrofit initiatives in Ireland have led to the improvement ofsignificant proportions of the existing housing stock. To date inIreland, approximately 300,000 of all 1.65 million homes havereceived some form of energy-efficiency retrofit upgrade primarilythrough the government-sponsored Better Energy Homes retrofitscheme [4]. Similar schemes in the UK have resulted in significantreductions in CO2 emissions and improvements in home comfort[19] [20]. The majority of these retrofit schemes have focused on‘shallow’ elemental measures such as the upgrade of heatingboilers/furnaces and the retention of heat through insulation ofinitially the loft/attic, and more recently, the whole buildingenvelope.

For private homeowners grant incentives are commonly avail-able for instigating these elemental measures. Large-scale financingof ‘deep’ whole-house packages of measures is not currentlyavailable and due to high costs of installation do not generally payback within reasonable time scales [20]. The upgrade of publichousing through social housing improvement programs in Irelandhas generally focused on envelope improvements. Thermal retrofitsaim to improve ceiling and wall U-values close to those stipulatedby building regulations for new builds. Insulation may be added tothe exterior or interior, or often in the cavity of a cavity-wall con-struction, common to Ireland and the UK.

2.2. Ventilation regulations in Ireland

Part F of the Irish (and UK) Building Regulations TechnicalGuidance Document [14] stipulates home ventilation levels. Theseare primarily defined for new build housing but may be used as thetarget for good practice retrofit also. Shallow retrofit generallyprovides for ventilation through the addition of background ven-tilators (Fig. 1) e a sleeved opening in the external wall, with adeflector or louvered covers. These background ventilators are alsocommonly known as ‘passive vents’ or ‘through-wall vents’.Ventilation airflow is driven through these vents predominantlydue to naturally-occurring pressure differentials across the ventsthemselves.

Limiting air permeability is a vague yet stated aim of Irish (andUK) building regulations, however only threshold levels are stipu-lated. Hence, retrofit commonly does not target building air-tightness but instead is focused on insulation. A reduction in airinfiltration can occur as an unintended consequence of insulationinstallation evenwhen air-tightness improvement is not the aim ofthe retrofit intervention [12]. A preceding study by one of the au-thors of this paper has documented reduced infiltration in homesafter insulation retrofit [13].

The 2009 edition of Part F [14] prescribes background ventila-tors with a combined equivalent area1 of 30,000 mm2 plus5000 mm2 for every 10 m2 of floor area above 70 m2. For single-

pressure difference as the vent being tested’ [14].

Fig. 1. (left) external view of louvered, passive wall vent, (middle) through-wall vent from Part F of UK regulations [15], (right) internal view of hit-and-miss vent evidencing paththrough wall.

O. Kinnane et al. / Building and Environment 106 (2016) 205e218 207

storey dwellings an additional 5000 mm2 should be provided.These equivalent areas apply to dwellings with an air permeabilitygreater than or equal to a threshold value of 5 m3/h/m2. Fordwellings below the threshold the equivalent area of the back-ground ventilators must be increased by 40%. Part F also stipulatesminimum equivalent areas of 2500 mm2 for kitchens, bathroomsand utility rooms; and 5000 mm2 for habitable rooms. Regulationsrecommend that to enable cross ventilation, a 10 mm gap isensured at the bottom of internal doors. UK regulations define TotalEquivalent Ventilator Area depending on house size, and number ofbedrooms. (35,000 mm2 for a 50 m2 house with 2 bedrooms or40,000 mm2 for a 90 m2 house with 2 or 3 bedrooms). In the ma-jority of cases similar equivalent areas result.

2.3. Ventilation in social housing

Social housing accounts for almost 10% of Ireland’s 1.65 millionhousing stock [27], and 17% of all UK homes [28]. Occupants ofsocial housing experience disproportionate economic pressuresdue to rising energy fuel costs. The problem of fuel poverty iswidespread in Ireland and the UK [29], particularly amongst theelderly in social housing [30]. Social housing is often overcrowdedand more continually occupied due to high unemployment ratesand/or higher age profiles amongst tenants [31]. Indoor environ-mental conditions for occupants can vary widely. Some are forcedto live in unhealthy cold conditions in efforts to save on high costsof heating energy. Other elderly or infirm occupants may havedistinct preferences [32] or physiological requirements and somemay heat their homes to high temperatures as a result. Socialhousing improvement programs are obliged to meet Part-F regu-lation, whereas private home owners may avoid exact abidance ofventilation requirements. Social housing might also be consideredto be disproportionally impacted by through-wall ventilation ashouses and rooms are generally of smaller proportion than privatehousing, and although this is accounted for by increasing equiva-lent ventilator area with floor area, it is not a linearly proportionalrelationship. These phenomena can result in occupant interferencewith ventilation systems in social housing including efforts toreduce cold air ingress through the blocking of vents [33] whichcould result in serious health risks.

The priorities of occupants, and the drivers of occupant behav-iour, in social housing (and indeed all housing) are many anddisparate [34,35]. Occupant feedback was obtained by Sinnott [13]at regular intervals before and after both thermal retrofit andinstallation of through-wall vents. In response to envelopeupgrading, occupants found their homes to bewarmer and easier toheat. However, there was widespread dissatisfaction with theinstallation of passive through-wall vents. Occupants complainedabout the introduction of new draughts crossing from room toroom, and vents dumping cold air from a high level or creatingdraughts around feet where vents are at a low level. An increased

and unacceptable level of street noise was also reported to transmitthrough the vents. In response a number of occupants took drasticaction to block or seal vents, as shown in Fig. 2. The goal of occu-pants in the main was the retention of heat, with little under-standing or care for the benefits of good IAQ in the home.

Ramos et al. [33] note that the actions of users often seems tocontradict the logic adopted in the design and that this subse-quently results in high variability in building performance. Due toeconomic pressures occupants of social housing may not prioritiseventilation and instead may aim to reduce energy consumption,retain heat and maintain comfort conditions. In principle theinstallation of background ventilators has the simple outcome ofthe provision of good ventilation. In reality, they result in heat loss,and thermal and audial discomfort. Occupants respond to theimposition of background ventilators with measures that can leadto inadequate ventilation and associated detrimental healthimpacts.

2.4. Ventilation metrics: effective ventilation and effectiveinfiltration

Later in this paper the Results and Discussion sectionwill centreon the ventilation metrics effective ventilation and effective infil-tration. In the interest of completeness, the two metrics will bedocumented here.

When the ventilation rate of a building changes over time,calculating the mean temporal ventilation rate is more complicatedthan simply taking the average of the air change rate. Thecomplication arises because indoor pollutant concentration is non-linear with respect to ventilation rate [36]. As such, the effectiveventilation rate is the appropriate metric for time-averaged, varyingventilation rates. The effective ventilation rate, ACHeff, is defined asthe steady-state ventilation that would yield the same averagepollutant concentration over some time period as the actual time-varying ventilation would in that same time period [37e40]:

ACHeff ¼1te

(1)

The turnover time, te, for each time step,i, is calculated as:

te;i ¼1� e�ACHiDt

ACHiþ te;i�1$e

�ACHiDt (2)

In Eq. (2) ACH is the air change rate of the house (/h) over thetime period Dt (h), and so te from Eq. (1) is the time-averagedturnover time. Using the effective ventilation rate allows us tomake direct comparisons with time-invariant ventilation rates,such as those stipulated by building regulations. Implications of theabove mean that in the modelling results section (below) theannual effective infiltration rate is presented e a special case of theeffective ventilation rate e rather than the simple annual mean

Fig. 2. Examples of blocked, (left) painted over, and (right) taped-over passive through-wall vents in two homes.

O. Kinnane et al. / Building and Environment 106 (2016) 205e218208

ventilation rate. (Note that within the context of this paper theterms effective ventilation and effective infiltration are used inter-changeably) Logue et al. [41] and Sherman et al. [42] demonstratedthat an annual time period is a suitable exposure period whenconsidering the dilution of continuously-emitted indoorcontaminants.

So that we can compare the annual effective infiltration ratewith a ventilation rate indicative of good IAQ, the general ventilationrate as defined in Part F is used as a target ventilation rate. Thegeneral ventilation rate, Qt , (in l/s) is the greater of either (a) 5 l/splus 4 l/s per person, or (b) 0.3 multiplied by the floor area of thedwelling in square metres.

3. Methodology overview

This study uses eight2 case-study social houses as the basis foranalysis. Field testing of these homes is documented by Sinnott[13], who describes an unintentional decrease in air permeabilityfollowing thermal retrofit of over 20%. Air permeability wasmeasured using blower-door tests conducted in accordance withISO standard 9972:2006 [43]. The houses are typical of Irish and UKsocial housing, i.e. small floor areas, leaky envelopes and poor levelsof insulation. All of the case-study houses are located in Co. Kil-kenny, Ireland. Fig. 3 (a) shows examples of a single-storey socialhousing typology of less than 50 m2 and the more common two-storey terraced house typology (b) with floor area of between 71and 90 m2. Both typologies are common to city and suburban lo-cations in Ireland and the UK.

All dwellings share the following characteristics:

� Load-bearing external cavity walls� Slab-on-grade construction� Solid-block internal walls on the ground floor� Suspended timber floors and stud-partitioned walls on the firstfloor (for the 2-storey houses)

� Cold-roof (non-conditioned) attics with pitched roofs� Double-glazed windows� Natural gas-fired, hydronic central heating system� Natural ventilation i.e. no whole-house mechanical ventilationsystem.

All homes underwent retrofit as part of the Social HousingImprovement scheme e a government sponsored scheme to

2 Note, Sinnott’s original study considered 9 case-study houses, however one ofthem has been omitted from this study as an outlier because the building’s airpermeability actually increased after the thermal retrofit interventions were per-formed, contrary to the rest of the sample. See Sinnott [13] for more details.

improve the efficiency of social housing in Ireland. This retrofitfocused on heating replacement, attic (300 mm fibre rolled) andwall insulation (100 mm full cavity fill) as well as remedial workaround windows and attic hatch. Table 1 documents the full set ofhouses according to their range of total floor area as outlined in PartF of the UK building regulations for sizing of equivalent ventilatorarea. Values for air permeability and exchange rates are docu-mented post thermal retrofit.

Following the thermal retrofit process, further ventilationretrofit measures were conducted to improve the compliance ofeach dwelling with Building Regulations 2009, Technical GuidanceDocument F e Ventilation [14]. The requirements varied bydwelling, but ventilation-related retrofit measures included:

� Installation of constant open louvered background ventilators inthe living areas

� Installation of ‘hit and miss’ background ventilators in all bed-rooms, so called as when the vertical slits line up, they ‘hit’ andwhen they don’t line up, they ‘miss’

� Installation of constant open background ventilators in thekitchen

� Installation of mechanical hood/range extract fans in the kitchen� Installation of mechanical extract fans in bathrooms.

To install the background ventilators, the external walls werecore drilled, sleeved with a 125-mm diameter internal PVC pipe,and then appropriate vent covers were attached.

Numerical modelling was used to investigate the impact ofinstalling Part F-compliant background ventilators on three of thecase-study dwellings on infiltration airflow rates after the thermalretrofit. Energy loads were subsequently simulated to evaluate theimpact of the installation of the background ventilators and variedinfiltration rates on the heating loads of the buildings. Simulationresults were validated using monitored energy loads from the case-study homes.

4. Numerical modelling

Simulations were performed to assess the impact of the Part-Fventilation retrofit on building IAQ and heating load for three ofthe case-study houses. CONTAMwas used for the airflowmodellinge an advanced airflow network and contaminant transport tooldeveloped at NIST [44]. CONTAM is primarily used to calculatemulti-zone building airflow rates and indoor contaminant con-centrations based on external wind pressures and buoyancy effectsdue to indoor/outdoor air temperature differences. CONTAM hasbeen extensively validated [45,46]. The EnergyPlus simulation en-gine [47] was used in conjunction with the proprietary front-endDesignBuilder v4 [48] to model the energy and heating loads.

Fig. 3. Examples of the (a) < 50-m2 House 1 and ground floor plan and (b) the ~90-m2 House 2, with ground and 1st floor plans.

Table 1Case study homes and their associated air-tightness level (adapted from Ref. [13]). Modelling case studies listed in bold.

Total floor area (m2) Orientation Q50 (m3/h.m2) /h (ACH @ 50Pa) Dwelling Label

�50 N-S 5.6 7.8 HN-S 4.4 6.1 J

71e80 E-W 13.8 14.0 CN-S 5.3 5.6 EN-S 8.3 5.3 FN-S 6.3 6.1 G

81e90 E-W 13.6 14.3 AE-W 10.2 10.9 BE-W 7.7 8.1 D

O. Kinnane et al. / Building and Environment 106 (2016) 205e218 209

CONTAM was used to calculate building infiltration rates. Theseinfiltration rates were then used as inputs to EnergyPlus/Design-Builder to calculate heating energy loads.

4.1. Simulation scenarios

Twomodelling scenarios were investigated for three of the case-study houses:

� Post-thermal retrofit e Scenario 1.

The houses are modelled after upgrade and installation of fabricinsulation with an inadvertent decrease in air permeability (in-crease in envelope air tightness). No additional ventilation open-ings have been installed.

� Post-ventilation retrofit e Scenario 2.

The houses have undergone thermal retrofit as in Scenario 1, butalso include installed background ventilators to ensure compliancewith Part F. The chimney inHouse 2 andHouse 3 has been convertedto a flue.

Scenario 1 may be considered as ‘before’ the ventilation retrofit

and Scenario 2 as ‘after’ the ventilation retrofit. All modelled homeshave an air permeability of >5 m3/h/m2 (threshold envelope airpermeability in Part F for vent sizes listed in Table 2). According toIrish regulations the total equivalent area of background ventilatorsrequired to comply with Part F is 35,000 mm2 for House 1(Afloor ¼ 50 m2), and 40,000 mm2 for House 2 and House 3(Afloor ¼ 90 m2). These equivalent vent areas also comply with UKregulations [15]. When viewed as a percentage of occupied floorarea the equivalent vent area for compliance with Part F is 0.07% offloor area for the case of the 50 m2 house, but only 0.04% for the90 m2 houses.

4.2. Airflow modelling

For both of the modelling scenarios infiltration airflows due tonatural pressure differences only are simulated, i.e. wind pressureand buoyancy effects. No mechanical airflows for either ventilationor indoor pollutant source control are modelled. There is no me-chanical pressurisation or depressurisation of the houses. Likewise,there is no natural ventilation (with the exception of the chimney inHouse 1) nor purge ventilation due to window and door opening.The modelling is intended to assess the ventilation contributionfrom infiltration and background ventilators only, and as such could

Table 2Properties for the three houses modelled using CONTAM. Note, Houses 2 and 3 are identical except for their envelope air permeability.

House property House 1 House 2 e (loose) House 3 e (tight)

Floor area (Afloor) 50 m2 90 m2 90 m2

Envelope area 170 m2 230 m2 230 m2

Volume 122 m3 234 m3 234 m3

Storeys 1 2 2Occupants 2 4 4Construction (post-thermal retrofit) General End-of-terrace, masonry, pitched roof. Constructed circa 1980.

Ceiling U-value 0.13W/m2K. 300 mm fibre rolled insulation (max. thermal conductivity 0.044W/m$K)External walls U-value 0.27 W/m2K. Double-leaf masonry wall. 100 mm filled cavity e pumped beaded

insulation (max. thermal conductivity of 0.033 W/m$K)Ground floor U-value: 0.64 W/m2K. Slab-on-grade. No change during retrofit.Windows U-value: 2.8 W/m2K. Double-glazed, air filled. No change during retrofit.

Chimneys/flues 1 1 1Envelope air permeability (post-thermal retrofit) 5.6 m3/h$m2 (@ 50 Pa) 13.8 m3/h$m2 (@ 50 Pa) 5.3 m3/h$m2 (@ 50 Pa)

7.7/h (ACH @ 50 Pa) 13.6/h (ACH @ 50 Pa) 5.2/h (ACH @ 50 Pa)Effective leakage area (AL) 187 cm2 630 cm2 243 cm2

Target ventilation rate (Qt)a 0.44/h 0.42/h 0.42/h

a Qt is the Part F whole-house target mechanical ventilation rate (see below).

O. Kinnane et al. / Building and Environment 106 (2016) 205e218210

be considered a worst-case ventilation scenario. Anecdotally, someoccupants of social housing, particularly amongst the elderly orinfirm, do not like to open windows at all for reasons of safety andsecurity, or consuming concerns to retain heat [13]. Therefore, theworst-case may sometimes be a reality.

In general, transient simulations were carried out using 5-mintime steps for one calendar year. The IWEC Kilkenny, Irelandweather file (see Fig. 4) was used to obtain outdoor air temperature,pressure, wind speed, wind direction and humidity. Indoor airtemperatures were assumed to be a constant 21 �C on ground floorsand a constant 22 �C upstairs to capture buoyancy effects. Airdensity was allowed to vary depending on air temperature. Modelcalculations were performed using a Newton-Raphson (N-R) algo-rithm (Simple Trust Region) to solve simultaneous non-linearequations of mass balance. Linear equations generated by the N-Ralgorithmwere solved using the Skyline algorithm. Formore detailson CONTAM and the airflow equations it uses, the reader is referredto the CONTAM User Guide [49].

Example houses with floor areas at the extremities of thosedocumented in Table 1 are modelled including House 1 (H) withfloor area (Afloor) of 50m2 and House 2 (A) and House 3 (E) both withfloor areas of 90 m2. House 2 and House 3 differ only in air

Fig. 4. Outdoor air dry bulb temperature and wind speed

permeability. Based on the monitored and field-tested houses inTable 1, House 2 has the loosest building envelope, while House 3represents the house with the tightest envelope. In the modellingstudy all three houses were assumed to be south facing for con-sistency of results. Table 2 outlines key parameters for themodelledhouses.

For all houses, a multi-zone CONTAM model was created basedon their physical geometry. The model for House 1 contains sixzones split over one storey: kitchen, hallway, living room, bath-room, bedroom 1 and bedroom 2. The models for House 2 andHouse 3 contain eight zones split over two storeys: kitchen, hallwayand living room (ground floor); landing, bathroom, bedroom 1,bedroom 2 and bedroom 3 (upstairs). In the case of House 2 andHouse 3, the hallway and landing are connected for airflow pur-poses via a staircase. All zones are assumed to be well mixed.

4.3. Airflow paths

For Scenario 1 the relevant dwelling airflow paths are open in-ternal doors, a chimney, a stairwell (House 2 and House 3), andenvelope permeability/leakage. Open doors were modelled be-tween rooms adjoining the hallways and landings. The doors were

for the simulation climate of Kilkenny (IWEC data).

O. Kinnane et al. / Building and Environment 106 (2016) 205e218 211

modelled as 2.1 m2 leakage areas following a power law with adischarge coefficient of 0.6 and a pressure exponent of 0.5. (SeeFlourentzou et al. [50]) A two-way flow model was not usedbecause the indoor air temperature was constant. All three houseshave a chimney located in the living area. The chimney wasmodelled as 29,000 mm2 leakage area with the same power-lawparameters as the doors. The stairwell between floors for House 2and House 3 were modelled as per Achakji & Tamura, i.e., a powerlaw with a cross-sectional area of 12.5 m2 and a pressure exponentof 0.5. Finally, envelope air permeability was modelled as acollection of small power-law leakage areas (or sites) withdischarge coefficients of 1 (4 Pa pressure drop) and pressure ex-ponents of 0.65. (See ASHRAE Handbook of Fundamentals ChapterF16 [40], Walker et al. [51] and Sherman and Chan [52] for dis-cussions on appropriate discharge coefficients and pressure expo-nents). The combined area of the individual leakage sites equals theeffective leakage area, AL, of the building envelope [40]. For eachhouse the envelope leakage sites are evenly distributed in heightand length over three walls. (All three houses have one shared wallwith an adjacent building, through which no airflowwas assumed).In total, House 1 has 24 leakage sites each with an area of 7800 cm2

(AL¼ 187,000mm2). The larger, leakier House 2 has 27 leakage sites,each with an area of 23,300 cm2 (AL ¼ 630,000 mm2), and thetighter House 3 also has 27 leakage sites with individual areas of9000 cm2 (AL ¼ 243,000 mm2).

For Scenario 2, the houses were modelled as per Scenario 1,except with the addition of background ventilators to all houses,and the conversion of chimneys to flues for House 2 and House 3.Compliance with Part F was achieved by adding background ven-tilators to the house models as per Table 3. The background ven-tilators were modelled as orifice openings following a power lawwith a discharge coefficient of 0.6 and a pressure exponent of 0.5.Note that Part F has no consideration of envelope air permeabilityexcept either side of the 5m2/h/m3 threshold, so House 2 and House3 both require the same total equivalent area of background ven-tilators to achieve compliance.

4.4. Energy modelling

Annual simulations were performed with DesignBuilder toquantify the energy impact of Part F compliance using backgroundventilators. The three case-study houses were simulated pre- andpost-ventilation retrofit as per Scenario 1 and Scenario 2 (above).An additional set of simulations were performed to ascertain theenergy performance of the case-study houses when ventilated atthe constant, whole-house rate prescribed by Part F (Qt).

The construction properties of the case-study houses are listedin Table 2. Infiltration is specified in air changes per hour (/h). Theimpact of airflow through the building envelope is modelled usinghourly infiltration rates determined using CONTAM, for thedifferent modelling scenarios and for the Part F-specified ventila-tion rate, Qt, (in l/s). The relative energy impact of air infiltrationwas assessed through an energy balance of building loads to assess

Table 3Equivalent areas of background ventilators per room, required for House 1, House 2 and H

Room Equivalent area (m

House 1 (2 bedroo

Kitchen 8220Hallway, Living room, Bathroom, Bedrooms 5417Landing e

Total equivalent area 35,305Total equivalent area required for Part F compliance 35,000

its overall impact on building energy load (Scenario E1).In accordance with DEAP e the Irish national assessment

methodology e the heating is scheduled to be on between 07.00and 09.00 in the morning and 17.00e23.00 in the evening. A gas-fired boiler powering a central heating system with radiatornetwork (typical in Ireland and the UK) was simulated. To ascertainthe baseline energy consumption of the houses, the buildings areinitially simulated with no infiltration or natural ventilationenabled. Hence heat losses are due primarily to conductive andconvective losses from the building envelope. Indoor temperaturesvary based on personal preference, socio-economic condition,health and behaviour. Varied indoor conditions were observedacross the set of case-study homes used as the basis for this study.To account for this diversity, the energy consumption is investi-gated for three thermal comfort scenarios (E1eE3). Note in thesesimulation scenarios, for consistency, all other parameters are heldconstant. Although the air change rate is non-linear with changingtemperature, the impact on energy consumption is neglible in thecontext of standard simulation errors.

E1 21 �C in downstairs living spaces and 22 �C in upstairs bed-rooms e the same temperatures settings as simulated in theCONTAM simulation study.

E2 18 �C average in all spaces e representative of lower indoortemperatures and looser control of thermal conditions in linewith varying adaptive comfort control [53], and approxi-mating temperatures that may be evident in under-heatedfuel poverty conditions [3] [54].

E3 21 �C in living spaces and 18 �C in bedrooms e indoor tem-peratures defined by the WHO for comfort conditions [55]and adopted into the Irish national assessment methodology.

E4 23 �C in all spaces e high indoor temperature profile some-times observed for elderly, infirm or housebound occupantswho may have distinct physiological characteristics in termsof thermal comfort and could be expected to heat theirhomes to higher temperatures as a result [56]. These con-ditions are consistent with a documented situation where asocial housing occupant maintained consistently high indoortemperatures due to chronic illness [13].

5. Results and Discussion

The subsequent section outlines the simulation results of theinvestigation of Part F-compliant through-wall ventilation. Theimpact on home ventilation of this uncontrolled, intermittent andweather-dependent passive ventilation strategy is assessed withreference to the controlled and regulation-specified target, whole-house ventilation rate, Qt. Calculated air exchange rates arecompared across European standards. The resulting energy penaltyusing passive ventilation is evaluated, and compared with the realmonitored energy load. This leads to discussion of alternativeventilation strategies adopted in European countries outside of theUK and Ireland.

ouse 3 to comply with Part F (Scenario 2).

m2)

ms) House 2 (3 bedrooms) House 3 (3 bedrooms)

8220 82205417 5417e e

40,722 40,72240,000 40,000

O. Kinnane et al. / Building and Environment 106 (2016) 205e218212

5.1. Airflow

Post-thermal and post-ventilation retrofit scenarios hourly airchanges and monthly effective ventilation rate profiles are shownfor the house case studies outlined.

5.1.1. House 1: 50 m2

Fig. 5 shows the whole-building, hourly air changes for House 1over the course of a calendar year, for both the post-thermal retrofitscenario (Scenario 1) and post-ventilation retrofit scenario (Sce-nario 2). Low infiltration airflows are observed in Scenario 1. Thetarget ventilation rate (Qt) for House 1 is 0.44/h. The annual effec-tive ventilation rate is only 0.22/h, meaning that when relyingsolely on infiltration for ventilation (plus natural airflow throughthe chimney), House 1 is consistently under-ventilated throughoutthe year when compared with a designed and controlled ventila-tion rate, as specified in Part F for whole-house mechanical venti-lation. Purpose-provided ventilation is required to increase theventilation rate to healthy levels.

Adding the background ventilators to House 1 to achieve Part Fcompliance (Scenario 2) increases the annual effective ventilationrate to 0.41/h. The increased effective ventilation rate is still belowthe target rate, but only by 7% over the course of the year. Withmechanical (or passive) exhaust specified in Part F for moisture-heavy rooms and the intermittent use of purge ventilation, thisshortfall is likely accounted for. Fig. 5 demonstrates the importanceof adding background ventilators to ensure that acceptable IAQ isachieved. Fig. 6 shows the monthly effective ventilation rate. ForScenario 1 the dwelling only comes close to the target ventilationrate in the early months of the year when natural ventilation

0 1000 2000 3000 4000Tim

0

1

2

3

4Scenario 1: ACH - 50m2

0 1000 2000 3000 4000Tim

0

1

2

3

4Scenario 2: ACH - 50m2

Fig. 5. Hourly air changes for House 1 (50-m2) for a cale

driving forces are highest. Addition of the background ventilatorshowever, increases the effective ventilation rate so that the targetrate is met throughout the year except in June and July when nat-ural ventilation driving forces are lowest. During summer months,low ventilation rates are commonly offset by higher levels of purgeventilationwhen occupants openwindow sections, as specified andrecognised in Part F.

5.1.2. House 2: 90 m2, looseFig. 7 shows the hourly air changes for the larger, leakier House

2. The target ventilation rate for House 2 is 0.42/h. The annualeffective ventilation rate for Scenario 1 is 0.65/h, meaning that evenbefore the background ventilators are installed the house is over-ventilated by 55% relative to the target rate. After installation ofthe background ventilators the annual effective ventilation rateincreases to 0.87/h emore than double the target rate. Again, theseairflow rates do not include source control or purge ventilationwhich would only increase the annual effective ventilation ratesfurther.

The monthly effective ventilation rates for House 2 (Fig. 8) showthat the target rate is exceeded throughout the year in both Sce-narios. The effective ventilation rate is over triple the target rate inJanuary after the installation of the background ventilators. Thehigh ventilation rates are coincident with the largest indoor/out-door temperature differences in the colder winter months (seeFig. 4).

The results suggest that installation of Part F-compliant back-ground ventilators is not required in House 2. The leakiness of thebuilding envelope means that there is already enough ventilationfrom infiltration without the background ventilators. The high

5000 6000 7000 8000e (h)

Post-Thermal Retrofit

Hourly building ACHAnnual mean effective infiltration rate (ACHeff)

Target ventilation rate (Qt)

5000 6000 7000 8000e (h)

Post-Ventilation Retrofit

Hourly building ACHAnnual mean effective infiltration rate (ACHeff)

Target annual ventilation rate (Qt)

HouHouHouHouHouHouHouHouHouHouHouHouHouHouHouHouHouHouHouHouHourlrlrlrlrlrlrlrrllrlrlrlrlrlrlrlrlrlrlrlyyyyyyyyyyyyyyyy buibuiubuiuibuibuibuibuibuibuibuibuibuibuibuibuibubuibuiu ldildidildldildildildildildildildildildildididildildidld ngnngngngngngngngngngngngngngngngnngngng AAAAAAAAAAAAAAAAAAAACHCHCHCHCHCHCHCHCHCHCHCHCHCHCHCHCHCHCHCHHAnnAnnAnnAnnAnnAnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnualualualualualualualualualualualualualualualualualualua meameameameameameameameameameameameameameameameameameameameannnnnnnnnnnnnnnnnnnnn effeffeffeffeffeffeffeffeffeffeffeffeffeffeffeffeffeffefffeeeeeeeeeeeeeeeeeeeeeccccccccccccccccccccttttttttttttiiiiiiiiiiiiivvvvvvvvvvvvvvvvvvvvveeeeeeeeeeeeeeeeeee infinfinfinfinfinfinfinfinfinfinfinfinfinfinfinfnfnfnfnfiltiltiltiltiltiltiltiltiltiltiltiltiltiltiltiltiltiltlttratratratratratraratratratratratratratratratratratratratrationionionionionionionionionionionionionionionionionionon ratratratratratratratratratratratratratratratratratratraatateeeeeeeeeeeeeeeeeee (A(A(A(A(A(A(A(A(A(A(A(A(A(A(A(A(A(A(A(A(ACCCCCCCCCCCCCCCCCCCCHHHHHHHHHHHHHHHHHHHHeeeeeeeeeeeeeeeeeeeffffffffffffffffffffffffffffffff ))))))))))))))))))

TarTarTarTarTarTaTarTarTarTarTarTaTarTaTarTaTarTarTarTargetgetgetgetgetgetgetgetgetgetgetgetgetgetgetgetgetgetgetge vvvvvvvvvvvvvvvvvvvententententententenentententenentnententenentententnttilailailailailailaailaalailailailailailailailaailatiotiotiotiotiotiotiotiotiotioootiotioiotiotioonnnnnnnnnnnnnnnnnnnn ratratratratrararararararaaraaraaararaa eeeeeeeeeeeeeeeeeeee (((((((((((((((((((QQQQQQQQQQQQQQQQQQQttttttttttt))))))))))))))))))

HouHouHouHouHouHouHouHouHouHouHouHououHouHouHouHouHouHouHouHouH rlrlrlrlrlrlrlrlrrlrlrlrlrlrlrrlrrr yyyyyyyyyyyyyyyyyyyy buibuibuibuibuibubuibuibuibuibubuibuibuibuibuibuibuibuibubu ldildildildildildildldildildildildildildldldldilddldd ngnngnngngnnngngngngngngngngngngngngng AAAAAAAAAAAAAAAAAAAACHCHCHCHCHCHCHCHCHCHCHCHCHCHCHCHCHCHCHCHCHAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnAnnnnualualuaualualualualualualualualuualualualualualuaualau meameameameameameameameameameaeameameameaeameaeameaeae nnnnnnnnnnnnnnnnnnn effeffeffeffeffeffeffeffeffeffeffeffeffefeffeffeffefeffeeeeeeeeeeeeeeeeeeecccccccccccccccccccctttttttttttttiiiiiiiivvvvvvvvvvvvvvvvvvvvveeeeeeeeeeeeeeeeeee infinfnfinfinfinfinfinfnfinfinfnfnfnfinfnfnfnfnffiltiltiltiltiltiltiltiltiltiltiltiltiltiltiltiltiltiltilti ratratratratratratratratratratratratratratratratratratrationionionionionionionioniononiononionionionionionionionon ratratratratratratratratratratraratratratratratratratraateeeeeeeeeeeeeeeee (A(A(A(A(A(A(A(A(A(A(A(A(A(A(A(A(A(A(A(A(ACCCCCCCCCCCCCCCCCCCCCHHHHHHHHHHHHHHHHHHHHHeeeeeeeeeeeeeeeeefffffffffffffffffffffffffffffffffffff))))))))))))))))))

TarTarTarTarTarTarTaraTarTarTarTarTarTarTaTarTTaTarTara getgetgetgetgetgetgetgetgetgetgetgetgetgetgetgetgetgetggetg annannannannannannannannannannannannannannannannannannana ualualualualualuauauauauauauauauauauauauaaua vvvvvvvvvvvvvvvvventententententententententententententententententenentilailailailailalailailailailalalailalalaatiotiotiotiotiotiotioiotiotiotiotioiotiotiotioottioonnnnnnnnnnnnnnnnnnnn ratratratatatratatratatatratatratatattatteeeeeeeeeeeeeeeeeee (((((((((((((((((((QQQQQQQQQQt)

ndar year. Results are for Scenario 1 and Scenario 2.

Fig. 6. Monthly effective ventilation rate for House 1 (50-m2) for Scenario 1 and Scenario 2.

Fig. 7. Hourly air changes for House 2 (90-m2 loose) house for a calendar year. Results are for Scenario 1 and Scenario 2.

O. Kinnane et al. / Building and Environment 106 (2016) 205e218 213

ventilation rates from the background ventilators will have energyimplications as throughout the year additional thermal energy willbe required to condition the surplus volume of cooler outdoorventilation air.

5.1.3. House 3: 90 m2, tightThe target ventilation rate for House 3 is 0.42/h. Fig. 9 shows that

the annual effective ventilation rate forHouse 3 in Scenario 1 is 0.27/h, or 36% under the target rate. Purpose-provided ventilation isrequired to increase the ventilation rate to healthy levels. Afterinstallation of the background ventilators the annual effective

Fig. 8. Monthly effective ventilation rate for House 2 (90-m2 loose) for Scenario 1 and Scenario 2.

Fig. 9. Hourly air changes for House 3 (90-m2 tight) for a calendar year. Results are for Scenario 1 and Scenario 2.

O. Kinnane et al. / Building and Environment 106 (2016) 205e218214

ventilation rate increases to 0.49/h, or 16% over the target rate.While House 3 has the same floor area as House 2, the tighterbuilding envelope means that there is a need for backgroundventilators in House 3 in order to maintain good IAQ. (Assuming no

window opening).Fig. 10 shows the monthly effective ventilation rates for House 3.

In Scenario 1 the target ventilation rate is only met in January, whileafter the installation of the background vents the target rate is met

Fig. 10. Monthly effective ventilation rate for House 3 (90-m2 tight) for Scenario 1 and Scenario 2.

O. Kinnane et al. / Building and Environment 106 (2016) 205e218 215

or exceeded for 11 months of the year.

5.2. Energy penalty

The heating energy load associated with the CONTAM simulatedindoor temperature conditions (E1 e 21 �C in living spaces, 22 �C inbedrooms) is plotted in Fig. 11 for the example of the 90 m2 house(House 2). Heating load per m2 of floor space is shown for the 0 to 1/h range of air change rates spanning target, pre and post ventilationretrofit (Scenarios 1 and 2). For contrast air change rates for otherthermal scenarios are also plotted as outlined. Indoor temperatureconditions vary for different residences depending on subjectivedesires, socio-economic status, age, illness and behaviour [13]. Forcomparison purposes other temperature settings are plottedincluding, approximate standard (E3 e 21 �C in living spaces, 18 �Cin bedrooms), high (E4 e 23 �C whole house) and low (E2 e 18 �Cwhole house) temperatures.

Similar to the results of Santos and Leal [18] a linear relationshipis documented between ventilation rate and heating energy usage.Occupants who desire high indoor temperatures due to disability,illness or pronounced sensation of cold discomfort face a significantenergy penalty particularly for high effective ventilation caused by

0

20

40

60

80

100

120

140

0 0.2 0.4 0.6 0.8 1

Hea

ng lo

ad (k

Wh/

m2/

yr)

/h air change

E1 - Living areas 21C,Bedrooms, 22C

E2 - Whole House, 18C

E3 - Living areas 21C,Bedrooms, 18C

E4 - Whole House, 23C

Fig. 11. Heating energy load for three comfort scenarios for House 2 with air changerates spanning the ranges calculated in earlier sections.

high air infiltration and the additional effects of passive vents.Table 4 shows the simulated annual heating loads for the test

houses in Scenarios 1 and 2, and also when ventilated at the Part Ftarget whole-house ventilation rate, Qt. To meet the target venti-lation rates the annual whole-house heating energy load for House1 is 2400 kWh and forHouse 2 andHouse 3 is 4500 kWh. The energypenalties in Table 4 are calculated for an indoor environmentassuming 21 �C in living spaces and 18 �C in bedrooms.

As the effective ventilation rate remains below the target, Qt, forHouse 1 no energy penalty is observed with the installation ofbackground ventilators. Similarly, the energy loads associated withventilation provision in House 3 - the tighter of the 90 m2 houses,are small. However, in houses with inherent poor airtightness theenergy penalty due to the installation of background ventilators issignificant. Post-thermal retrofit an annual effective ventilation rate(Scenario 1) of 0.65/h is observed in the leaky House 2 due primarilyto its poor airtightness. This high ventilation rate results in a sig-nificant increase in heating load, of 24% over the load at the targetventilation rate. When background vents are added during theventilation retrofit the heating requirement increases to 47% abovethe baseline case.

5.3. European context

To assess the ventilation rates observed in this study withrespect to European regulation and standards, values are comparedwith those documented by Brelih and Seppanen [57] in a studyfrom the European-wide ventilation study ‘HealthVent’ [58]. Stan-dards relating to ventilation levels in Europe are set by the Euro-pean Committee for Standardisation (CEN) although these are notgenerally harmonised with levels in national regulations [57].Instead, ventilation rates vary widely across Europe as outlined inFig. 12 for the range of countries analysed. The ventilation rates ofHouse 2 and House 3 for the post-thermal retrofit and post-ventilation retrofit scenarios are shown in Fig. 12 in comparisonto European levels.

A minimum air change rate of 0.5/h is often referenced inventilation and health literature as a general benchmark forensuring adequate ventilation and good health [59] [60] [61] [62].The BRE in the UK showed that 68% of homes had whole-house airchange rates less than 0.5/h [63], although the whole-house

Table 4Heating energy loads for post-thermal retrofit (Scenario 1) and post-ventilation retrofit (Scenario 2) scenarios, at 21 �C in living spaces and 18 �C in bedrooms.

House 1 House 2 House 3

Qt Scenario 1 Scenario 2 Qt Scenario 1 Scenario 2 Qt Scenario 1 Scenario 2

Air changes (/h) 0.44 0.22 0.41 0.42 0.65 0.87 0.42 0.27 0.49Heating load (kWh) 2400 1900 2300 4500 5600 6600 4500 3800 4800Heating load (kWh/m2) 48 38 47 50 62 73 50 43 54

Fig. 12. Ventilation rates for House 2 for before (Scenario 1 e S1) and after (Scenario 2 e S2) installation of passive through wall vents.

O. Kinnane et al. / Building and Environment 106 (2016) 205e218216

mechanical ventilation rate specified in Part F, here taken as thetarget rate, is 0.42/h. In the context of European ventilation levelsHouse 2 with poor airtightness, has close to the highest ventilationrate on the European scale, due to its infiltration alone. This isexacerbated when through-wall vents are added. The more airtightversion of the 90 m2 house (House 3) approximates a ventilationrate of 0.5/h but continues to exhibit over-ventilation with respectto the target ventilation rate (Qt).

The goal of residential-sector energy reduction is high on theEuropean agenda. Considering this, the practice of backgroundventilation as a specified means of home ventilation, in Ireland andthe UK, requires revaluation. Although it offers a cheap installationoption, air provision is variable, often significantly above and belowtarget levels. Compensation of heat loss through auxiliary spaceheating results in significant additional energy loads. An alterna-tive, and German-recommended, basic passive ventilation solution,Stoßlüften (literally ‘shock ventilation’, or ‘airing’ in English), isproposed to be up to 20 times more efficient than consistent trickleventilation via tilted window openings as is commonly used byGerman occupants [26]. The Stoßlüften method involves regularwhole-house shock ventilation viamanual full-windowopening forbrief periods. Using a simple calculation, Galvin quantifies the en-ergy impact for this method of passive ventilation at 550 kW h (perheating season in 87 m2 apartment [26]). Although the method ofcalculation is simple and the method of ventilation very different, acursory comparison between the German and Irish/UK methods ofventilation provision shows the energy impact to be much lowerthan for a similarly-sized home from this study.

Alternative enhanced ventilation methods that ensure consis-tently adequate air change with low associated energy loads areavailable, but some are prohibitively costly. Mechanical heat re-covery ventilators (MHRV) offer one option, and can be installed atrelatively low cost. In whole-house retrofits MHRV, when aligned

with retrofit heat pump systems, have been shown to be expensive[20]. A large number of existing and emerging ventilation systemspurport to save energy, provide adequate and controlled airflow intandem with improved comfort for new build and retrofit sce-narios, at lower investment costs. Using demand-controlledventilation in new residential buildings, heating requirements forventilation air, and electricity consumption for the ventilation fan,were decreased by 20% and 30% [64]. There is still limited knowl-edge surrounding in-situ operating effectiveness of the range ofalternative systems. Anecdotally, occupants have been known toturn off mechanical systems to ‘save energy’ and there are issuessurrounding their cleaning and maintenance.

It is clear that the provision of passive wall ventilation as part ofa retrofit programme can have a number of drawbacks. Inappro-priate ventilation can impact comfort conditions and, as shown byother studies, potentially the health of the building and its occu-pants when not designed and managed correctly. To mitigate therisk of poor design in the future there is a need to developknowledge of newer systems, particularly for retrofit scenarios.Hybrid strategies that balance mechanical and natural ventilation[16] seems appropriate for temperate climates, and for the nature ofresidential living. It has been proposed by authors investigatingclimate change that uncontrolled natural ventilation alone is likelyto be insufficient to maintain indoor thermal conditions withinacceptable limits into the future [65]. Designing for this reality nowwill save repeated retrofit intervention in future years. It should benoted however, for both nowand into the future, that a ‘one size fitsall’ approach is unlikely to be most effective.

6. Conclusions

The strategy of through-wall passive ventilation, generally, orinstalled as part of a retrofit program, is shown to have a significant

O. Kinnane et al. / Building and Environment 106 (2016) 205e218 217

impact on ventilation rates and on thermal energy loads in thehome. In relatively airtight homes infiltration alone is not sufficientto provide for regulation-required air changes, and purpose-provided ventilation is necessary. However, when complying withpassive vent sizes specified in building regulations (Part F), housingcan be significantly over ventilated particularly in homes with poorairtightness. Part-F does not adequately account for buildingairtightness when specifying through-wall vent sizing and this hasconsequences for comfort conditions and thermal energy loads inthe home. For occupants of social housing the regulations areparticularly burdensome, resulting in high energy costs tocompensate for over-ventilation.

When evaluated with reference to controlled ventilation ratesspecified in regulations, the case study social housing underassessment range from a close adherence, to a massive over-shootof ventilation rates, dependent on the inherent airtightness of thehouse. Over-ventilation of double the target rate is observed insocial housing with high infiltration rates. This results in highadditional heating loads (þ45%) to maintain indoor air tempera-tures at comfortable levels. Although homes of similar size andconstruction vary significantly in levels of airtightness (see Table 2),Part F does not take this into account and instead specifies commonvent sizes.

Expressions of thermal discomfort by house occupants, duedirectly to the passive through-wall vents, seem well founded. Thevents have a significant effect onwhole-house heating loads and, aspreviously reported, a dramatic impact on comfort conditions inindoor spaces [13]. However, occupant interaction with vents canbe detrimental to ensuring good air quality in the home. The pre-sent strategy and sizing methodology of through-wall vents mightbe seen to provoke these actions, when occupant focus is under-standably on heat retention and associated financial saving.

This study shows the practice of uncontrolled, passive, back-ground ventilation to be at odds with the goals of energy efficiencyin the residential sector by showing high heating loads are neces-sary to compensate for high building air change rates. It shows awide range of building air change results when this strategy ofventilation is sized without reference to building airtightness. Aretrofit practice that would focus on achievement of a good level ofhouse air tightness would help reduce occurrence of over-ventilation and heat loss when passive background vent sareinstalled. Greater occupant confidence in the controlled efficiencyof their ventilation system would potentially result in a reducedtendency to tamper with room vents and detrimentally affectventilation.

Acknowledgements

William Turner is funded under Programme for Research inThird Level Institutions and co-funded under the EuropeanRegional Development Fund (ERDF).

References

[1] European Parliament, Directive 2010/31/EU of the European Parliament and ofthe Council of 19 May 2010 on the Energy Performance of Buildings (Recast),2010. http://www.eceee.org/policy-areas/buildings/EPBD_Recast/EPBD_recast_19May2010.pdf.

[2] B. Lapillonne, C. Sebi, K. Pollier, Energy Efficiency Trends for Households in theEU, Enerdata e An analysis based on the ODYSEE database, 2012.

[3] J.D. Healy, J.P. Clinch, Quantifying the severity of fuel poverty, its relationshipwith poor nmbnnbnbbnnb housing and reasons for non-investment inenergy-saving measures in Ireland, Energy Policy 32 (2004) 207e220.

[4] E. Dennehy, M. Howley, Energy in the Residential Sector, Sustainable EnergyAuthority of Ireland, Dublin, Ireland, 2013. http://www.seai.ie/Publications/Statistics_Publications/Energy-in-the-Residential-Sector/Energy-in-the-Residential-Sector-2013.pdf.

[5] Office of National Statistics e UK greenhouse gas emmissions, Provisional

Figures and 2010 UK Greeenhouse Gas Emissions, Final Figures by Fuel Typeand End User, Department of Energy and Climate Change, London, 2011.

[6] U.S. EPA, The inside Story: a Guide to Indoor Air Quality. (6609J), 2016(accessed June 15, 2016), https://www.epa.gov/indoor-air-quality-iaq/inside-story-guide-indoor-air-quality.

[7] J. Sundell, On the history of indoor air quality and health, Indoor Air 14 (2004)51e58, http://dx.doi.org/10.1111/j.1600-0668.2004.00273.x.

[8] WHO, WHO Guidelines for Indoor Air Quality: Dampness and Mould, WorldHealth Organisation, Copenhagen, Denmark, 2009. http://www.euro.who.int/__data/assets/pdf_file/0017/43325/E92645.pdf.

[9] L. Mølhave, M. Krzyzanowski, The right to healthy indoor air, Indoor Air 10(2000) 211. http://www.ncbi.nlm.nih.gov/pubmed/11089325.

[10] D. Campbell, Asthma Could Be Worsened by Energy-efficient Homes, WarnsStudy, Guard, 2015. https://www.theguardian.com/society/2015/sep/20/energy-efficient-homes-could-worsen-asthma.

[11] J. Milner, C. Shrubsole, P. Das, B. Jones, I. Ridley, Z. Chalabi, et al., Home energyefficiency and radon related risk of lung cancer: modelling study, BMJ 348(2014), http://dx.doi.org/10.1136/bmj.f7493 f7493ef7493.

[12] C. Shrubsole, A. Macmillan, M. Davies, N. May, 100 Unintended consequencesof policies to improve the energy efficiency of the UK housing stock, IndoorBuilt Environ. 23 (2014) 340e352, http://dx.doi.org/10.1177/1420326X14524586.

[13] D. Sinnott, Dwelling airtightness: a socio-technical evaluation in an Irishcontext, Build. Environ. 95 (2016) 264e271, http://dx.doi.org/10.1016/j.buildenv.2015.08.022.

[14] Minister for the Environment Heritage and Local Government (Ireland),Ireland Building Regulations, Technical Guidance Document, Part F e Venti-lation, 2009, 1647,en.pdf, http://www.environ.ie/sites/default/files/migrated-files/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad.

[15] Department for Communities and Local Government, UK Building Regula-tions, Approved Document, Part F e Ventilation, 2010. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/468871/ADF_LOCKED.pdf.

[16] W.J.N. Turner, I.S. Walker, Using a ventilation controller to optimise resi-dential passive ventilation for energy and indoor air quality, Build. Environ. 70(2013) 20e30, http://dx.doi.org/10.1016/j.buildenv.2013.08.004.

[17] M. Liddament, M. Orme, Energy and ventilation, Appl. Therm. Eng. 18 (1998)1101e1109, http://dx.doi.org/10.1016/S1359-4311(98)00040-4.

[18] H.R.R. Santos, V.M.S. Leal, Energy vs. ventilation rate in buildings: a compre-hensive scenario-based assessment in the European context, Energy Build. 54(2012) 111e121, http://dx.doi.org/10.1016/j.enbuild.2012.07.040.

[19] R. Gupta, M. Gregg, S. Passmore, G. Stevens, Intent and outcomes from theretrofit for the future programme: key lessons, Build. Res. Inf. 43 (2015)435e451, http://dx.doi.org/10.1080/09613218.2015.1024042.

[20] P. Jones, S. Lannon, J. Patterson, Retrofitting existing housing: how far, howmuch? Build. Res. Inf. 41 (2013) 532e550, http://dx.doi.org/10.1080/09613218.2013.807064.

[21] A. Byrne, G. Byrne, A. Davies, A.J. Robinson, Transient and quasi-steady ther-mal behaviour of a building envelope due to retrofitted cavity wall and ceilinginsulation, Energy Build. 61 (2013) 356e365, http://dx.doi.org/10.1016/j.enbuild.2013.02.044.

[22] W.J.N. Turner, I.S. Walker, Advanced Controls and Sustainable Systems forResidential Ventilation (LBNL-5968E), 2012. http://epb-dev.lbl.gov/sites/all/files/lbnl-5968e.pdf.

[23] M.H. Sherman, I.S. Walker, Air distribution effectiveness for different me-chanical ventilation systems, Int. J. Vent. 6 (2008) 307e313, http://dx.doi.org/10.1080/14733315.2008.11683786.

[24] J.S. Park, H.J. Kim, A field study of occupant behavior and energy consumptionin apartments with mechanical ventilation, Energy Build. 50 (2012) 19e25,http://dx.doi.org/10.1016/j.enbuild.2012.03.015.

[25] A. Roetzel, A. Tsangrassoulis, U. Dietrich, S. Busching, A review of occupantcontrol on natural ventilation, Renew. Sustain. Energy Rev. 14 (2010)1001e1013, http://dx.doi.org/10.1016/j.rser.2009.11.005.

[26] R. Galvin, Impediments to energy-efficient ventilation of German dwellings: acase study in Aachen, Energy Build. 56 (2013) 32e40, http://dx.doi.org/10.1016/j.enbuild.2012.10.020.

[27] Pre Budget Submission, Irish Council for Social Housing, 2013, 2014.[28] Department for Communities and Local Government, English Housing Survey

e Headline Report 2014 to 2015, 2016. London, UK, https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/501065/EHS_Headline_report_2014-15.pdf.

[29] UK Department of Energy & Climate Change, Annual Fuel Poverty StatisticsReport, 2015. London, UK, 2015, https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/468011/Fuel_Poverty_Report_2015.pdf.

[30] E. Webb, D. Blane, R. de Vries, Housing and respiratory health at older ages,J. Epidemiol. Community Health 67 (2013) 280e285, http://dx.doi.org/10.1136/jech-2012-201458.

[31] S.M. Tabatabaei Sameni, M. Gaterell, A. Montazami, A. Ahmed, Overheatinginvestigation in UK social housing flats built to the Passivhaus standard, Build.Environ. 92 (2015) 222e235, http://dx.doi.org/10.1016/j.buildenv.2015.03.030.

[32] O. Kinnane, T. Grey, M. Dyer, Perceptions of thermal environments in de-mentia friendly dwellings, in: 9th Wind. Conf. Mak. Comf. Relev., Windsor, UK,2016. https://www.researchgate.net/publication/299834586_Perceptions_of_

O. Kinnane et al. / Building and Environment 106 (2016) 205e218218

thermal_environments_in_dementia_friendly_dwellings.[33] N.M.M. Ramos, R.M.S.F. Almeida, A. Curado, P.F. Pereira, S. Manuel, J. Maia,

Airtightness and ventilation in a mild climate country rehabilitated socialhousing buildings e what users want and what they get, Build. Environ. 92(2015) 97e110, http://dx.doi.org/10.1016/j.buildenv.2015.04.016.

[34] T. Hong, S. D’Oca, S.C. Taylor-Lange, W.J.N. Turner, Y. Chen, S.P. Corgnati, Anontology to represent energy-related occupant behavior in buildings. Part II:implementation of the DNAS framework using an XML schema, Build. Envi-ron. 94 (2015) 196e205, http://dx.doi.org/10.1016/j.buildenv.2015.08.006.

[35] T. Hong, S. D’Oca, W.J.N. Turner, S.C. Taylor-Lange, An ontology to representenergy-related occupant behavior in buildings. Part I: introduction to theDNAs framework, Build. Environ. 92 (2015) 764e777, http://dx.doi.org/10.1016/j.buildenv.2015.02.019.

[36] W.J.N. Turner, M.H. Sherman, I.S. Walker, Infiltration as ventilation: weather-induced dilution, HVAC&R Res. 18 (2012) 1122e1135, http://dx.doi.org/10.1080/10789669.2012.704836.

[37] M.H. Sherman, D.J. Wilson, Relating actual and effective ventilation in deter-mining indoor air-quality, Build. Environ. 21 (1986) 135e144.

[38] G.K. Yuill, The variation of the effective natural ventilation rate with weatherconditions, in: Proc. Sol. Energy Soc. Canada Rewnewable Energy Conf, Can-ada, Winnipeg, 1986, pp. 70e75.

[39] G.K. Yuill, The development of a method of determining air change rates indetached dwellings for assessing indoor air quality, ASHRAE Trans. 97 (1991)896e903.

[40] ASHRAE, ASHRAE Handbook-fundamentals, 2013.[41] J.M. Logue, T.E. McKone, M.H. Sherman, B.C. Singer, Hazard assessment of

chemical air contaminants measured in residences (vol 21, pg 92, 2010), In-door Air 21 (2010) 351e352, http://dx.doi.org/10.1111/j.1600-0668.2011.00724.x.

[42] M.H. Sherman, J. Logue, B. Singer, Infiltration effects on residential pollutantconcentrations for continuous and intermittent mechanical ventilation ap-proaches, HVAC&R Res. 17 (2011) 159e173, http://dx.doi.org/10.1080/10789669.2011.543258.

[43] ISO, ISO Standard 9972:2006 Thermal Performance of Buildings e Determi-nation of Air Permeability of Buildings e Fan Pressurization Method, 2006.

[44] NIST, CONTAM, vol. 3.1.0.3, 2013. http://www.bfrl.nist.gov/IAQanalysis/index.htm.

[45] F. Haghighat, A.C. Megri, A Comprehensive validation of two airflowmodelsdCOMIS and CONTAM, Indoor Air 6 (1996) 278e288, http://dx.doi.org/10.1111/j.1600-0668.1996.00007.x.

[46] F. Haghighat, H. Li, Building airflow movement e validation of three airflowmodels, J. Archit. Plann. Res. 21 (2004) 331e349.

[47] US DOE, EnergyPlus, 2015. http://apps1.eere.energy.gov/buildings/energyplus/.

[48] DesignBuilder Software Ltd., DesignBuilder 3.0, 2012. http://www.designbuilder.co.uk/content/view/43/64/.

[49] G.N. Walton, W.S. Dols, CONTAM Online User Guide, 2013 (accessed May 29,

2015), http://www.bfrl.nist.gov/IAQanalysis/docs/CONTAM_31.pdf.[50] F. Flourentzou, J. Van der Maas, C.-A. Roulet, Natural ventilation for passive

cooling: measurement of discharge coefficients, Energy Build. 27 (1998)283e292, http://dx.doi.org/10.1016/S0378-7788(97)00043-1.

[51] I.S. Walker, D.J. Wilson, M.H. Sherman, A comparison of the power law toquadratic formulations for air infiltration calculations, Energy Build. 27 (1998)293e299, http://dx.doi.org/10.1016/S0378-7788(97)00047-9.

[52] M.H. Sherman, W.R. Chan, Building Airtightness: Research and Practice, 2004,pp. 1e46.

[53] G.S. Brager, R.J. de Dear, Historical and cultural influences on comfort ex-pectations, in: R.J. Cole, R. Lorch (Eds.), Build. Cult. Environ, Blackwell Pub-lishing Ltd, 2003, pp. 177e201.

[54] E. Monahan, Thermal Comfort, Energy Usage and Fuel Poverty in a Sample ofOlder Person’s Households in Dublin, Dublin Institute of Technology, 2014.http://arrow.dit.ie/cgi/viewcontent.cgi?article¼1089&context¼scienmas.

[55] W.H.O, (WHO), Housing, Energy and Thermal Comfort: a Review of 10Countries within the WHO European Region, 2007.

[56] SHCS, Scottish House Conditions Survey, Technical Note: Definition andMeasurement of Fuel Poverty in SHCS, 2013. Edinburgh, UK, http://www.gov.scot/Resource/0046/00465627.pdf.

[57] N. Brelih, O. Seppanen, Ventilation rates and IAQ in european standards andnational regulations, in: Proc. 32nd AIVC Conf. 1st TightVent Conf., Brussels,2011.

[58] HealthVent e Healthvent, Http://www.healthvent.byg.dtu.dk. (n.d.).[59] C. Dimitroulopoulou, Ventilation in European dwellings: a review, Build. En-

viron. 47 (2012) 109e125, http://dx.doi.org/10.1016/j.buildenv.2011.07.016.[60] O.A. Sepp€anen, W.J. Fisk, M.J. Mendell, Association of ventilation rates and CO2

concentrations with health and other responses in commercial and institu-tional buildings, Indoor Air 9 (1999) 226e252. http://www.ncbi.nlm.nih.gov/pubmed/10649857.

[61] P. Wargocki, J. Sundell, W. Bischof, G.W. Brundrett, P.O. Fanger, F. Gyntelberg,et al., Ventilation and health in non-industrial indoor environments: reportfrom a European multidisciplinary scientific consensus meeting (EUROVEN),Indoor Air 12 (2002) 113e128. http://www.ncbi.nlm.nih.gov/pubmed/12216467.

[62] O.A. Seppanen, W.J. Fisk, Summary of human responses to ventilation, IndoorAir 14 (2004) 102e118, http://dx.doi.org/10.1111/j.1600-0668.2004.00279.x.

[63] C. Dimitroulopoulou, D. Crump, S. Coward, B. Brown, R. Squire, H. Mann,Ventilation, Air Tightness and Indoor Air Quality in New Homes. BR477, BREBookshop, Garston, 2005.

[64] A. Hesaraki, S. Holmberg, Demand-controlled ventilation in new residentialbuildings: consequences on indoor air quality and energy savings, Indoor BuiltEnviron. 24 (2015) 162e173, http://dx.doi.org/10.1177/1420326X13508565.

[65] A. Mavrogianni, J. Taylor, M. Davies, C. Thoua, J. Kolm-Murray, Urban socialhousing resilience to excess summer heat, Build. Res. Inf. 43 (2015) 316e333,http://dx.doi.org/10.1080/09613218.2015.991515.