Design risks to comfort and health of occupiers | Architects Journal


3 November 2016

The implications of increased thermal performance, airtightness in dwellings and the consequent dangers of poor ventilation due to inadequate design input are the subject of much discussion at present. The following article from the UK Architects Journal outlines some of the challenges facing designers.  The comments section links to an article on the same topic by Irish author Kate de Selincourt in Passsive House+ magazine (see PH+ article here).  The BRegs Blog thought the title of the AJ article was a TYPO little misleading, so we have inserted a more appropriate header:

[Poor Ventilation] blamed for health risks in homes

55 homes inspected in UK study and only 2 had adequate ventilation

“As homes become increasingly fuel-efficient, the resulting lack of clean, fresh air could create serious health risks, reports Colin Marrs

Throughout the past year a slew of reports has been published that raise serious questions about the safety of new-build homes. Increasingly stringent building regulations aimed at reducing carbon emissions are resulting in new houses that are ever more airtight. While this helps reduce fuel consumption, the burden is on architects to ensure that occupants of new homes can breathe clean and fresh air. Recent evidence suggests that the construction industry, designers included, is failing to meet this challenge.

Paul Harrison, an independent toxicologist and member of a working group on air quality created by the Royal College of Physicians, describes serious health risks associated with poor ventilation systems. ‘Sick building syndrome describes a variety of symptoms including headaches, allergies, reduced productivity, a sore throat and dry skin,’ he says. ‘In addition, poor air quality can provoke asthma.’

‘If things have gone seriously wrong with ventilation, then it can kill’

Paul Harrison, independent toxicologist

Even more dangerously, dirty air can lead to the incomplete combustion of carbon fuels in appliances such as gas boilers, warns Harrison. A resulting increase in carbon monoxide levels can have serious effects on the human nervous system and even lead to death. ‘If things have gone seriously wrong with ventilation, then it can kill,’ he says.

A new, as yet unpublished, study for the Department for Communities and Local Government (DCLG), carried out by engineering consultancy AECOM with building performance firm Fourwalls, starkly demonstrates the issue. Last winter, it monitored 55 airtight homes using either natural ventilation or decentralised mechanical extract ventilation systems to discover whether they met minimum ventilation provisions set out in Approved Document F (ADF) – Means of Ventilation under 2010 revisions to the Building Regulations.

The study found that, of the 55 homes visited, only two fully met the guidance. The majority of cases where pollutant levels were poorer than ADF recommendations used mechanical systems, with most of these delivering less than half of the recommended air extraction rates outlined in the guidance. The DCLG will consider the report before deciding whether it needs to change the regulations.

In March, one of the last reports published by the disbanded Zero Carbon Hub revealed serious problems with the installation of mechanical ventilation systems. Not one of the six sites its research team visited delivered systems that met minimum standards.

How much responsibility must architects take for these problems?

But how much responsibility must architects take for these problems, and what can be done to improve the potential threat to human health?

James Pickard, director at Cartwright Pickard Architects, questions whether architects are taking seriously enough the impact of their designs on the comfort and health of occupiers.

Last year, Cartwright Pickard and the Mackintosh Environmental Architecture Research Unit produced another study showing that improved energy efficiency in our homes may be having unintended consequences for occupants’ health (AJ 07.08.15).

‘How many could genuinely say, with hand on heart, that they have any interest in ventilation?’ he says. ‘The highest accolades in the profession often go to buildings that have been proved to have problems. As long as they look good and get on the cover of a magazine, we don’t care about how they work.’

Architect Lynne Sullivan, chair of the RIBA’s sustainable futures group, blames a disconnect between concept and detailed design stages. ‘Sometimes the architect hasn’t thought about or been told by the client what sort of ventilation system should be used,’ she says. ‘To design a ventilation system properly requires careful integration with the spatial design and the way the system weaves through the house. We need to do these things at the right time otherwise we, as architects, are complicit in any failure.’

Tom Dollard, head of sustainable design at Pollard Thomas Edwards, says the amount of responsibility that should be taken by an architect depends on the size of the project. ‘For small extensions and one-off house projects the architect won’t have a mechanical and engineering (M&E) consultant,’ he says. ‘They won’t be designing the system in detail but are coordinating it and need to understand it. If not, they won’t only get into trouble from a performance point of view but also in terms of the aesthetics of where the fans come out of the walls.’

’A developer will select a ventilation strategy to help with carbon compliance rather than ventilation’

Ian Mawditt, Fourwalls director

For bigger projects, he says, architects need to get better at co-ordinating with the

M&E consultant. ‘Sometimes we issue our drawings, they do theirs and that doesn’t get co-ordinated back as well as it should do,’ he says. ‘Or their designs might not work – they might not know there is a structural column in the way, for example. Architects need to realise this is a problem and speak to the relevant specialists to work with them.’

Fourwalls director Ian Mawditt says the Building Regulations intended to guide the design of new homes are failing to encourage this type of thinking. Ventilation is included as part of the Standard Assessment Procedure (SAP) used to measure and compare the energy and environmental performance of homes. But, says Mawditt, ‘SAP is not intended as a design tool. A developer will essentially select a ventilation strategy to help with carbon compliance rather than ventilation.’

The Zero Carbon Hub report also found it ‘unlikely’ that systems failing to meet building standards would ever be discovered by building control officers. Its research team ‘found examples of commissioning testing procedures and checks not being properly carried out and commissioning sheets not being scrutinised, with no comeback’.

Adequate inspection of completed ventilation systems is all the more vital because it is often difficult for occupiers to realise they have a problem, says Mark Siddall, principal architect at Durham-based low energy practice LEAP.

’Homeowners don’t always know there is a problem with air quality because it is not something you can see’

Mark Siddall, LEAP principal architect

‘As a homeowner, you are not properly equipped to identify what is going on,’ he says. ‘You might have seen reduced bills due to better insulation, but you don’t always know there is a problem with the air quality because it is not something you can see.’

In other cases, occupants only pick up on issues because of the noise made by fans working overtime to combat low air-flow rates. The Zero Carbon Hub report found that nearly all of the 13 occupants interviewed by its team had turned off their mechanical ventilation systems because they were too loud, especially at night – defeating their object. ‘The higher the resistance, the harder the fans have to work and the more noise occurs,’ Farr says.

Problems with ventilation systems can also be caused by a fragmentation in responsibilities, argues Mawditt. ‘A heating engineer might be responsible for designing the system and connecting pipes to the boiler, but a plumber will install the pipes and an electrician might connect the boiler. Nobody has overall responsibility,’ he says.

This division of labour is more likely to cause issues in the UK because of the reduced role of the architect in signing off projects, says Siddall. ‘In the US, Germany and other countries, the designer holds a lot more liability, so if installation is inadequate, it is their responsibility,’ he says. ‘In the UK there is a process of palming off responsibility; developers tend to say: “Oh well, building control will look at that.”’

Even where systems are designed well, cost-cutting can lead to short cuts on the building site, such as the substitution of products with cheaper versions. Pickard says that, in particular, replacing solid ducting with flexible ducting can lead to poor performance and the possible build-up of moisture in the system. ‘We all know how shambolic building sites can get,’ he says. ‘If a site foreman is running late and over-budget, he will pay for the cheapest, nastiest kit, and pay any Tom, Dick and Harry to install it.’

Justin Bere, director at Passivhaus specialist Bere Architects says: ‘It is logical to suggest that because some people do bad installations, and get away with it, regulations around design and installation should be toughened and penalties imposed in order to ensure that people apply the necessary skill and effort to do the job properly.’

Replacing solid ducting with flexible ducting can lead to poor performance and moisture build-up

In 2009, the Prince’s Foundation designed its Natural House at the BRE Campus, deliberately taking a low-tech approach, using a demand-controlled passive stack ventilation system, combined with breathable clay bricks walls.

Ben Bolgar, senior director at the Prince’s Foundation for Building Community, says: ‘The initial capital outlay and the longer-term maintenance cost of systems such as the passive vent one used in the Natural House is overall significantly lower than that of mechanical systems. To add to that, the conventional systems draw energy throughout their lifetime – energy which costs money.

‘So, for good air quality, the passive ventilation system should be lighter on the pocket.’

But even with ventilation systems that rely on natural ventilation methods, occupier behaviour can cause issues, says Tim Sharpe, professor in environmental architecture and director at Glasgow’s Mackintosh Environmental Architecture Research Unit. He points to a study by the Building Research Establishment which tested homes fitted with trickle vents. ‘This concluded that all the homes were fine,’ he says, ‘but a follow-up study found that 60 per cent of the vents were closed by residents once they were occupied.’

Despite the overall poor picture, Mawditt says the design and installation of mechanical ventilation systems is slowly improving. ‘In some developments by in-house teams employed by large housebuilders we are starting to see dotted lines on structural drawings showing where ducting should be routed,’ he says. ‘Going back five years ago, those lines wouldn’t be there and the builders would only work out they needed to make provision when they were on site. But it will take a few more years for it to fully filter through.’

An improvement in the design of ventilation systems is undoubtedly overdue. Currently, an inadequate inspection regime allows the construction of homes that are potentially dangerous to their occupants’ health. Architects have a leading role to play in designing buildings with systems that are easier to operate and maintain. But changing the status quo will require proactive investment in solutions that work, widespread dissemination of best practice, and a less grudging approach from an industry notoriously resistant to changes that will affect its bottom line.

Other posts of interest:

Part L compliance – Who wants a building control service provided by cowboys?

Notes from the (thermal) edge: Part L Compliance (2 of 2)

Part L | DECLG slowdown: Better building or more red-tape?

Is there a regulation for thermal bridging condensation risk? | Part L

Part L compliance issues – S.I.9 (1 of 2)

Part L- is compliance worth the paper its written on?

SI.9 and Part L | Specialist ancillary certifiers Part 2

SI.9 and Part L | Are specialist ancillary certifiers needed? Part 1

Design Certifiers – 3 things about certifying Part L…

3 thoughts on “Design risks to comfort and health of occupiers | Architects Journal

  1. Michael O'Neill

    Reply to – Design risks to comfort and health of occupiers – Architects Journal

    Ventilation systems are designed by specialist HVAC Engineers. Making sure the ventilation system is designed correctly is the architect’s prerogative, not designing the system itself.

    The effects on the design of internal spaces do need to be considered by the Design Team as a whole. However, even if the architect has done further specialized study in ventilation, the detail design and specification should be left to the relevant and established engineering discipline.

    As dwellings become more highly serviced, the Design Team will need to include appropriate these disciplines. This will have its own effect on HVAC design. HVAC Engineers will need to become more aware of comfort and energy saving compliance and not merely be satisfied with crunching the numbers and balancing the system.

    Better delivery and extract systems will be required offering lower noise and fewer drafts from improved diffusers that are much closer to occupants heads than they are in commercial, civic or public buildings

    As services are a significant cost of any building, the future uses of building may need to be considered, especially in an Urban context where the building use may change many times over the life of the building.

    Admirable as the developing focus on the subject is we cannot lose sight of the fact the unintended consequences here may be far greater than lessened air quality. There is more to consider than Parts L and C

    What effect will a badly designed installation have on sound transmission?
    How do we prevent the transmission of cold smoke fumes and gases around the building?
    Do 30min FR vent covers exist to preserve the integrity of the upper floors in dwellings?
    Are 30min FR closable vents available to prevent a developing fire spreading?

    There is a growing body of opinion that the increasing incidence of asthma and allergic reactions in developed countries is now being attributed to raising our children in an environment that is too clean. It seems that, as human organisms, we need challenges to test our systems, in order to develop strengths we will need through our lives.

    What happens next? Will someone use a HEPA filter as a means of protecting against airborne spores and viruses? If we now enclose our children in these hermetically sealed. temperature regulated houses, will we end up with a generation unable to deal with colds or flu bugs or sudden drops in temperature?

    Who benefits?

  2. Jenny power

    This is not a good article. It is hysterical in tone and has already been castigated in other forums as having an incorrect headline: ventilation is the question, not airtightness. Buildings built to compliance standard whereby ventilation requirements are balanced with increased airtightness simply don’t suffer this misinformed consequence.

  3. Michael Tweed

    One of the most basic requirements in an enclosed space occupied by people is to replace the air made stale though carbon dioxide and moisture build-up caused by the people themselves. In the design of a building such as a large open plan office designing a ventilation system tailored to the space is relatively simple. The activities of the people occupying the space will most likely be very similar, that being sedentary work at a desk. The design can also be tailored to the “average” person since statistically averaging all the occupants will probably match that average.
    Houses are quite different. The number of occupants, their ages and physiques are all unknown and changeable factors. Similarly the way the space is used and the amount of daily occupation are also unknown. For this reason it is impractical to provide anything other than a broad brush approach to home ventilation, whatever form that home might take. Designing a ventilation to tight parameters will only work in a small number of cases. This is why I have such a problem with the whole notion of air-tightness. Bear in mind this is Ireland, a wet, temperate island constantly affected by the Gulf Stream. We rarely have severe cold temperature for long periods. Our average winter temperature is around 8deg C and our humidity is high since no matter what the wind direction, the air is travelling over large bodies of water and consequently carries air borne moisture.
    The high humidity is why good ventilation is so vital. In Irish homes airborne moisture builds up far more rapidly than carbon dioxide and the ventilation system must be able to keep airborne moisture levels low to avoid condensation and mould growth. The high humidity of the external replacement air is one of the factors which make this so difficult in our climate when relying on natural ventilation to do the job.
    The best “broad brush” design principle for good ventilation which I’ve come up with is the rule-of-thumb that a home should have a ventilation rate of one complete air change every two hours. It doesn’t take much calculation to work out what this mean in litres of air per second since the starting premise is that this is a “broad brush” design. So exact floor area calculations are pointless! Assuming the floor area to the nearest 5sqm is perfectly adequate. Similarly assume the floor height is 2.5 metres. So for example a typical four bedroom house might be two storeys high – an approximate height of 5 metres. Each storey area might be say 60sqm. So the volume of air in the house is 300 cubic metres. One air change every two hours equates to an air flow of 150 cubic metre per hour or about 42 litres per second. Now just take a moment to imagine that! What we easily forget is that air is a substance which just happens to be invisible to us. But imagine stacking 42 litre cartons of milk on a table and visualise changing them for another 42 litres every second. Now you can begin to understand the amount of air flow you need 24/7/365 to ventilate this 120sqm house.
    Let’s pause to consider this. Technical Guidance Document (TGD) L requires all this work to make the home airtight but to make the home habitable and comfortable and free from condensation you now have to let at least 42 litres of air flow through the home EVERY SECOND.
    Then there is the nonsense in the current TGD F Ventilation.
    There you will find meaningless calculations regarding the size of natural ventilation openings. The rate of flow of the air is determined by TWO factors and the cross section area of an opening is only ONE of these factors. The other is the speed of the air through the opening and the speed of the air depends on the air pressure difference on either side of the opening. Because air has a certain “solidity” it requires a force to make it flow! That force is air pressure difference. TGD F completely ignores this, which is why all the calculations are a nonsense.
    If you put up a building there will be different air pressure differences on all four sides. Sometimes these differences will be quite significant, depending on numerous factors such as wind speed, shape of the building, shelter from surrounding buildings and landscape, micro-climate etc. And sometimes of course the air pressure differences will be insignificant and almost non-existent. They are as inconsistent and unpredictable as our climate, because they are dependent on the climate! Therefore the air flow through air vents in the walls will be inconsistent and unreliable. It is impossible to predict natural air flow through vent openings at a design stage. So we make a home airtight and then we provide completely inconsistent and unreliable ventilation by putting in some openings designed to spurious size calculations! Sometimes the air blasts through the vents like a jet engine, other times no air flows at all. Genius!
    In the past we built houses that leaked air and almost invariably had an open chimney flue. Of course these houses required significant amounts of fuel to heat because of this, but they were certainly well ventilated and there were fewer problems with condensation and mould. Of course people accepted that their homes would be colder in the winter and they would simply wear more layers of clothing! How arrogant are we to expect to live this far north on our planet and to sit around watching tv in mid-winter in light t-shirts!
    The only reliable ventilation system that I’ve come across for homes is a heat recovery ventilation system where the air flow is controlled by mechanical means and rather than dumping those 42 litres of heated air every second and replacing them with 42 litres of cold fresh air from outside, much of the heat is recovered using a simple plate heat exchange chamber to warm the fresh incoming air.
    Architecture at its most basic is simply the solution to a problem. When designing a home one of the elements of the problem is ensuring the comfort of the occupants. Therefore good ventilation must be part of the solution. In the article a question is posed “how much responsibility must architects take for (the ventilation) problems?” The architect is fully responsible. Whether he solves the problem himself or with the assistance of other experts such as mechanical engineers is irrelevant.


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