October 11th, 2019

New-build homes: why some owners are left feeling the cold

Newly built homes are more energy efficient than ever, the government said this week. But thousands of buyers are finding that their expensive new homes are cold and draughty with heating bills far higher than expected. The culprit? The finger of blame is pointing towards builders rushing to meet targets, lax standards and poor inspection, with badly installed dry lining at the heart of the issue.

Dry lining became popular in the UK in the 1980s, replacing traditional “wet” plastering with ready-made plasterboard attached to walls and ceilings. It means plastering can be done in a couple of days rather than weeks.

There is nothing intrinsically wrong with dry lining, which is used commonly in Scandinavia and North America, where winter temperatures drop far below those of Britain. It gives a smooth finish and can be decorated straight away.

cold house

 But what thermal imaging surveyors and other building experts are discovering is that widespread poor installation of plasterboard has resulted in the airtightness suffering badly.

Housebuilders rush to meet targets (their own and the government’s), often cutting corners, and airtightness suffers as a result. The plasterboard is attached to masonry with adhesive. But Paul Buckingham, a thermal imaging surveyor, says housebuilders often cut costs using “dot and dab” adhesive, rather than solid dabbing.

Thermal imaging often finds air pockets behind plasterboard walls, causing cold spots and reduced thermal efficiency.

“We don’t see any of this airflow in old houses,” he says. “In those built in the 60s and 70s, with concrete floors, the airtightness is pretty good.” (However, they may leak air elsewhere – through open trickle ventilators or fireplaces.)

Going even further back, case studies undertaken in 2011 by energy consultant Diane Hubbard found that most of the houses built before 1900 were more airtight than expected, and in some cases better than required by the 2006 building regulations, and “modern extensions may not be as airtight as the original building”.

To ensure new homes pass air leakage tests – mandatory in England and Wales since 2006 – some developers may seal gaps with mastic or decorator’s caulk. But this will deteriorate, and carpet fitters often remove it around skirting boards.

Buckingham and Ian Jones, another thermal imaging surveyor, say tests are often “bodged” in this way. This can render energy efficiency ratings meaningless. Between them they have tested thousands of new homes in recent years, and say virtually all leak air, to a greater or lesser extent.

2017 research paper by Dr Jenny Love and others from UCL Energy Institute, which analysed results from 144,024 homes tested under the ATTMA (Air Tightness Testing & Measurement Association) scheme, came up with similar findings.

“The result of meeting the target through temporary sealing, which fails after a short time, is that for most of a dwelling’s lifetime, air permeability will be higher than the design value,” the paper said.

NHBC, the main standard-setting body and warranty provider for new homes, says it is not aware of the use of mastic or other fillers to ensure air leakage tests are met.

Barry Cope of the ATTMA says building regulations are too lax. The maximum allowed leakage is the equivalent of a 20p-sized hole in every square metre of wall – “a huge amount of air leakage” – which gives an air test result of 10. New homes usually aim for a reading below five, while a passive house is close to zero.

In addition, the regulations allow sample testing, which means a large number of new homes are never tested. The quality of air testing – the lack of proper training and qualifications – is another issue. A test costs from £170 plus VAT.

Cope says: “With building regulations not likely to change in the near future, it is difficult to try to convince some housebuilders that spending that bit of time doing the work to a much higher standard is worth the ever so slight reduction in profit

Leave a Reply

Copyright Eco Building Systems © 2020