The Concrete Centre questions research findings

The Concrete Centre has examined a recent report conducted by the UK Timber Frame Association (UKTFA).

In the report by the UKTFA, 'Comfort and Cost', the timber industry demonstrates the expected costs of achieving the higher levels of the Code for Sustainable Homes against a background of rising temperatures to 2080.

The Concrete Centre says that a number of design assumptions and misconceptions undermine the research findings.

Tom de Saulles, building physicist, The Concrete Centre explained: "The difference in thermal mass between new build masonry and new build timber frame construction is not a significant factor affecting either thermal comfort or energy consumption, now or within the lifetime of the building.

"In fact, the thermal mass provided by masonry construction is becoming an increasingly important aspect of housing design, as it helps ensure summertime comfort in our warming climate".

"Even a moderate amount of thermal mass can improve comfort in hot conditions, a fact supported by CIBSE Guide TM36 which deals with climate change adaptation".

"Thermal mass can also improve energy efficiency during the heating season, and if used effectively in housing design will achieve a worthwhile amount of energy savings over a building's lifetime", said de Saulles.

"This is can be seen by modelling standard house types using the draft SAP 2009 tool, which takes fuller account of thermal mass than the current version of SAP which will be replaced next year".

The Concrete Centre would agree that thermal mass is one of several elements affecting comfort, but in extreme summer conditions the main adaptation measures available to timber frame, are unlikely to be enough to keep a home comfortably cool.

The research suggests doubling the plasterboard in timber frame homes, but this will have a limited effect since it only increases the thermal mass of an external wall from 9 kJ/m2K to 18 kJ/m2K, compared to the 60 to 190 kJ/m2k available in masonry walls.

"Even if you double the plasterboard, it will still have three times less thermal mass than that of an aircrete wall with dryling", continued de Saulles.

"Also with a timber frame dwelling there is no option of having a concrete first floor which can contribute significantly to the overall thermal mass.

The research also highlights the benefits of air tightness in delivering energy efficient housing and claims that it is easier to make a dwelling airtight using timber frame than masonry".

"This is not the case, and it is important to note that there are many tested examples of extremely airtight masonry housing, both demonstration and non-demonstration, which use a robust air barrier to ensure long-term air tightness with no concerns regarding movement, twisting or dimensional stability".

"Furthermore, it is unfortunate that the research does not give due attention to whole live costs".

"Other areas conveniently overlooked include maintenance issues, durability, fire risk, flooding, rot and infestation.

"Thermal mass is one of the elements affecting comfort"".

"It is good that this is recognised by the timber industry but their argument of needing very little does not stand up to scrutiny", concluded de Saulles.

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