MUSEUMS AND GALLERIES MUSEUMS AND GALLERIES

42 November 2018 www.acr-news.com

The majority of indoor environments are able to

tolerate small variations in humidity and temperature

with no ill eff ects for the occupants – for example,

a relative humidity (RH) range of 40-60% is acceptable for

most workplaces.

This is not the case, however, for spaces that house

delicate objects such as those typically found in museums

and galleries. There are also a number of other objects that

may not be considered delicate, but require a controlled

environment to prevent deterioration.

A case in point is vintage vehicles and, indeed, newer

vehicles that are being stored for extended periods. Vehicles

are particularly vulnerable to damage to bodywork and

interior fabrics due to high humidity. High moisture levels

can accelerate corrosion of metallic surfaces, and a build-up

of moisture in fabrics accelerates degradation and may even

lead to mould growth.

Historically, the approach in these applications has been to

use heating to ensure the air doesn’t fall below a particular

temperature. However, experience shows that controlling

humidity through dehumidifi cation, rather than by simply

heating the space, is far more eff ective at protecting the

vehicles, whilst also optimising energy effi ciency.

How this achieved is largely determined by the size of the

space. In a large storage space, desiccant dehumidifi ers are

the ideal solution. Models range from free-standing mobile

units to larger bespoke designs, with drying capacities from

0.6 kg/hour to 162 kg/hour and air volumes up to 24,000

m³/hour. These also provide a low level of heating that

supports the dehumidifi cation process and helps to gently dry

vehicles that have been garaged whilst still wet from rain.

For smaller spaces, refrigerant dehumidifi ers are usually a

more cost-eff ective option for preventing the degradation of

vehicles.

There are many other situations that may not be typically

considered as ‘close control’ applications, but will benefi t

from maintaining RH within a relatively narrow range.

For example, several top hotels in London have fi tted

humidity control systems to their wine cellars to prevent the

corks from drying out, as well as in their humidors to keep

cigars in perfect condition. Similar principles apply to the

houses and apartments of the well-to-do - to protect their

furs, works of art and antique furniture.

And if they happen to be rock superstars they may well

require humidity control to protect guitars, harpsichords

and other sensitive stringed instruments. Considerably less

common was a recent request to control humidity in a space

where natural coral was on display, to maintain its natural

colours.

Outside the building, estates with orangeries and

orchard rooms require not just the very best glasshouse

technology but also very precise humidity control to simulate

Mediterranean conditions and enable their exotic plants to

fl ourish.

Arts and antiquities

The art of humidity controlWhile eff ective humidity control is important for any indoor environment, it has particular signifi cance for spaces housing fragile or historic items – as well as some items that aren’t typically considered as delicate. John Barker of Humidity Solutions explains

MUSEUMS AND GALLERIES

www.acr-news.com November 2018 43

Heron Hill

As well as the less obvious examples cited above,

there are many applications with a clear need for

close control of RH.

Arts, antiquities and other delicate objects

are particularly vulnerable to damage resulting

from fluctuations in the indoor environment –

especially any wide swings in temperature and

humidity. Wood, for example, is particularly prone

to expansion or shrinkage if it is not stored in

a humidity-controlled environment. Any such

movement of the wood may cause cracking,

separation of different wood layers and will

also destabilise any paint or other finishes that

have been applied to the wood. Additionally,

the finishes themselves may be subject to

deterioration when exposed to low or high

humidity.

High humidity may also lead to condensation

on metallic, stone or other objects with cold

surfaces, potentially causing significant damage.

Stabilising the relative humidity in any such

storage areas will help to prevent any defamation

or cracks and ensure they maintain the same

dimensions. In doing so, in compliance with

BS5454, the RH should be maintained in the

range 40-65% (+/-5%), with temperatures in

the range 16-19°C (+/-1°C). As well as ensuring

protection of the objects, compliance with this

standard will help to meet the requirements of

insurance companies or benefactors loaning works

of art.

Staying in controlThe UK climate dictates that most problems

relating to humidity are due to low RH, creating

a requirement for humidification – though some

projects will require both humidification and

dehumidification and different times of the year.

The important thing is to fully understand each

project’s requirements – there are no ‘off the

shelf’ solutions for these types of applications.

For instance, if the space is open to the public

there will be considerable variation in line

with fluctuating visitor numbers. Each person

contributes moisture to the air in their exhaled

breath, and if it’s been raining they may also be

evaporating water into the air from their clothes.

In parallel, their body temperature will contribute

to an increase in room air temperature.

Consequently, systems serving areas with

variable occupancy – or subjected to non-

tempered air from outside for ventilation – will

need to incorporate continuous monitoring by

humidity sensors and be able to respond quickly

to changes in RH. However, many such venues

do not have staff experienced in humidity

control, so there is growing demand for remote

monitoring, where system operation can be

monitored, via the ‘cloud’, by humidity control

specialists. Not only does this ensure a quick

response to any deviation from acceptable

environmental parameters, it also helps to inform

a cost-effective planned maintenance regime

based on actual plant usage.

As well as the usage of the space, the best

solution for each project will also be influenced

by factors such as budgets, lifecycle costs, the

client’s attitude to sustainability/carbon reduction

and the nature of the building itself. For instance,

we were required to devise very different

solutions for the Tate Modern (housed in a former

power station), Tate Liverpool (a converted

warehouse) and Tate Britain, which was designed

as a gallery from the start.

Demanding humidity control applications

demand a combination of specialist expertise and

experience of a range of different project types.

For that reason, it makes sense to call on support

from a supplier that has no ties to a particular

manufacturer and can offer a tailored solution

using the most appropriate products.

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