Good News for the Traditionally Built! – old walls perform far better than expected

Results from the first stage of SPAB’s (The Society for the Protection of Ancient Buildings) research on the energy efficiency performance of old buildings suggest that standard U-value calculations used across the construction industry underestimate the thermal performance of traditional walls. In some instances, it now appears that heat loss through vernacular materials can be up to three times lower than expected.

The initial study (click here to download) and audio visual discussion (view here) suggests that conventional industry practices are struggling to accurately represent the thermal performance of traditionally built walls. Ultimately, this could have negative consequences for historic buildings as calculated theoretical U-values (suggesting a poorer performance) may lead owners and professionals to adopt disproportionate energy saving interventions that may not only be unnecessary, but also invasive and potentially harmful to the fabric of a building.

SPAB’s report, written by Dr Caroline Rye, MSc student at the University of Portsmouth, compared the in-situ U-values (U-value is the universally known unit to describe the rate of heat transmittance or loss through a wall / roof / floor etc) of various traditional vernacular walls against the theoretical U-value for these walls using the class-leading BuildDesk U 3.4 software. Importantly, the theoretical value obtained from the U-value calculations is used by professionals as the base-line for assessing thermal performance of different types of constructions. However, SPAB’s on-the-spot research suggests that 79% of the traditionally built walls sampled – including walls of timber, cob, limestone, slate, and granite – actually perform better than expected.

Even taking into account a possible error margin of up to 10%, SPAB’s findings show that old buildings may not be as energy inefficient as the building industry has generally understood them to be.

This SPAB research is not a criticism of the calculation methodology or U-value modeling software, but it does highlight the difficulty of modeling and calculating the thermal performance of traditional walls using conventional techniques.

Jonathan Garlick, SPAB Technical Officer and project leader explains: “Amazingly, this research has not been carried out before in England. Accepted theoretical performance figures have long been used as a standard base measurement by professionals and homeowners when old buildings are being up-graded, altered or even assessed for Energy Performance Certificates, but are they correct?  We believe that with some traditional materials our in-situ results prove that they are not. We appear to be actually underselling the thermal performance of our old buildings by not fully understanding them.”                                                                                                                                         

“Energy efficiency is becoming the key issue for people working with historic buildings. If we aren’t basing our approaches on the right figures to begin with, then we could, unintentionally, be doing untold, invasive damage.”

The initial objective of the SPAB research project was to develop the work begun by Historic Scotland and English Heritage.  Historic Scotland has just produced a report (Tech Paper 10 - U Values & Traditional Buildings), looking mainly at the performance of sandstone construction, while English Heritage is currently looking at brick construction. SPAB felt a responsibility to represent other nationally important traditional walling types such as, wattle & daub paneling, cob, limestone, slate, granite etc. These traditional materials often get overlooked, but, from a historical perspective, they probably have the most to lose in terms of standard assessment.

Jonathan Garlick continues: “It’s all about understanding the building first – how it performs, how we use it and how we live in it. U-values are not the complete story. Energy efficiency is also about our behaviour in a building, moisture content in the structure, humidity, temperature, air-tightness, the quality of the air we breathe. These are all issues that we intend to consider in further stages of the project.”

SPAB’s energy efficiency project continues throughout 2011. Research is already underway on air-tightness, moisture and air quality.  Later this year the team will return to buildings constructed from traditional materials that were first assessed in an ‘as found’ state and which have since been upgraded to enhance their energy performance.  In an effort to relay the results as quickly as possible a SPAB Technical Day (Old Building Energy Efficiency Research: The Latest Thinking & Results Update) has been organised for 18th October 2011. All are welcome.

Jonathan Garlick says: “We believe that this important research will at last reveal some fascinating and useful information to help people make beneficial, effective and appropriate decisions about their old buildings without the need to destroy historical fabric or harm the indoor environment in the process.”

Roger Curtis, Historic Scotland’s Head of Technical Research added: “We hope that this research will build on our existing knowledge of the thermal performance of traditional building elements and develop our understanding of energy efficiency. In this way we hope to be able to make more sensitive and considered interventions to improve their thermal performance.”

If any organisations or individuals would like more information or would like to become involved with this on-going project SPAB would be delighted to hear from them. Please contact SPAB on 0207 456 0906 for more information.  Ends                                                                                                                             

For images and media information contact Kate Griffin, SPAB press office, 0207 456 0905, email:                                                                                                                                                                                                                               

Notes to Editors

To download a copy of the SPAB Research Report 1 (U-Value Report), go to: 

For visual information and to listen to Jonathan Garlick and Dr Caroline Rye discuss the project, go to:

For course information on our Technical Days please contact Claire Martin at or call 020 7456 0915

For more information about SPAB, advice and other publications go to

For more information on Historic Scotland’s work on energy efficiency and the technical papers, please go to:

BuildDesk U 3.4 – U-value and Condensation Risk Analysis software by BuildDesk Ltd: for more information contact Steve Channon on 01656 869940 or visit

SPAB is Britain’s oldest building conservation body. It was set up by William Morris to oppose the destructive restorations of the Victorian era and promote the alternative of “conservative repair”. By law it must be notified of applications to demolish listed buildings in England and Wales and comments on hundreds each year. Today its broad remit is to advise, educate and campaign.  The Society also trains architects and craftsmen; produces a range of helpful publications and campaigns on issues like VAT.  It also has a separate section devoted to Mills.