Time to let in some fresh air on standards for low-energy homes

Ventilation and its importance to the health of owners of new housing is being overlooked at our peril

he measures announced in the budget for first-time buyers of new homes end up working — and it’s a big if, as housing lecturer and Move columnist Lorcan Sirr argued in these pages last week — we’ll see a massive and rapid uplift in house building, virtually from a standing start.

What will these new homes be like in terms of build quality? Although the Building Control (Amendment) Regulations should force the new homes to comply with building regulations, there are reasons to be worried. There will be cold comfort for new-home owners if their building meets compliance, yet still fails, as a result of flaws in the regulations.

While we shouldn’t guess what approaches developers will take, we have a remarkably good idea of how new homes have been built over the past few years. That’s because the Sustainable Energy Authority of Ireland, to its immense credit, has published the national building energy rating research tool, a database of every BER and provisional BER yet published. (Provisional ratings are required for new homes not yet built but being sold off the plans).

This database doesn’t just include the energy rating scores: it also includes much detailed information about each dwelling — from age of construction, to insulation levels, heating system type and efficiency, and much, much more.

Changes to building regulations that were introduced in December 2011 mean that all new homes have to be designed to use 60% less energy than homes built to 2005 standards, which on average translates to a mid A3 BER. So how are the homes in the database faring?

Remarkably well, at first glance. The average BER score is 59 kWh/m2/yr — an A3 BER, and not far from the A2 target of less than 50 kWh/m2/yr. The insulation standards for walls, floors and roofs all exceed the backstops for passive house design in Ireland, while the windows aren’t far off either.

The average airtightness test result, which measures unintended leakage through constructional defects, is coming in at 3.7m3/hr/m2 at 50 Pa. This is about six times worse than the passive house target, but it’s also about three times better than the average new home was achieving during the boom.

This is all pretty heartening, but one aspect of these homes makes my heart sink: ventilation. Of these homes, 63% are reliant on so-called “natural” ventilation, which amounts to drilling holes in walls — a maddeningly backwards approach that is permitted in the regulations, in spite of being unsupported by evidence.

Last year, perhaps the most authoritative analysis to date of the relationship between ventilation and health was published: What does the scientific literature tell us about the ventilation-health relationship in public and residential buildings?, by Carrer et al.

The paper analysed 168 research studies on ventilation and health, whittling it down to 48 that were deemed most relevant and conclusive. While the results for mechanical ventilation were broadly positive, albeit with many caveats, the report includes comments on natural ventilation which bear repeating:

Ventilation rates in naturally ventilated buildings can be characterised only with a high level of uncertainty because they depend on outdoor conditions and activities and on the behaviour of building occupants.

Instantaneous (spot) measurements or even weekly averages may not be able to capture and represent the true variability and may not be representative of actual rates. Consequently, exposures that are related to ventilation may not be properly estimated and may not reflect the actual exposures. They may simply be too low or too high, when compared with the actual levels.

How can you legislate for a ventilation approach when you have no idea whether it will under or over-ventilate the building? As a UK Department of Communities study on 20 naturally ventilated homes revealed, occupants had blocked 60% of the total number of vents, presumably to prevent uncomfortable drafts and save money on heating bills, indicating that with natural ventilation, all roads may lead to under-ventilation.

Mercifully the EU is alive to the issue, warning member states in July that, without due care, the transition to low-energy buildings might compromise indoor air quality, and calling for ventilation standards to be improved simultaneously with energy efficiency. It’s imperative the government heeds this warning to get its house in order on ventilation, and fast, or today’s first-time buyers could become tomorrow’s health crisis.

Jeff Colley is the editor of Passive House Plus magazine; passivehouseplus.ie