The Walker Timber Val-U-Therm® building system was used by Lindum Construction for the first domestic new build properties in the East Midlands to receive the PassivHaus certificate. The properties are part of the affordable housing development for emh (East Midlands Housing) Group at Hart Lea, in Sandiacre, Derbyshire.
- A fabric first approach inspired by the PassivHaus Standard
- Used the Val-U-Therm wall system with a U-value of 0.09W/m2K
- Actual air testing results across the site ranging from 0.46h-1 to 0.58h-1 at 50Pa – all plots achieved PassivHaus standards
- Enhanced construction detailing to achieve a SAP y-value <0.05W/m2K
- Total cost of the build just under £1,400 per m2
- Finalist in the Cost & Build-ability category for the UK PassivHaus Awards 2014.
Philip Haines – Resident noted,” I just can’t praise it enough, so much different to our old house, never go back to the original old sort of houses, these are absolutely superb.”
The Client Perspective:
The site, which was formerly a care home, has been redeveloped to create much needed affordable homes consisting of 5 two bedroom houses, 2 three bedroom houses and 2 two bedroom bungalows (1 of which is to full wheelchair adapted standards). All the homes have been built to an equivalent build specification with 3 properties receiving the formal PassivHaus accreditation.
Having recent experience of building to varying Code Levels, emh were already aware of the potential pitfalls associated with achieving compliance with the energy requirements. Poor integration of low carbon technologies, high maintenance issues, dwellings not performing as expected and homes having higher bills than predicted; were all problems that emh are keen to avoid in their new build schemes going forward. Based on these experiences, it was clear that the favoured approach would be to adopt a fabric first build specification that would enable the scheme to achieve the required energy performance without the need for any bolt on renewables.
A PassivHaus inspired fabric first approach was compared against the more commonly adopted and high-tech approaches, including integrated low carbon technologies; ground and air source heat pumps, and bolt on renewables; solar PV and solar thermal. Whole life costs and benefits of each option were evaluated and highlighted to demonstrate lifetime performance which should always be a key deciding factor for social housing providers who have a long term vested interest in their building stock.
Description of Project:
The site had already been submitted for planning and there was a need to be onsite within a specific timeframe in order to draw down the funding from the HCA. So by this time the scheme was already constrained in terms of site layout and building design. Analysis carried out in PHPP (PassivHaus Planning Package) showed that certification would be achievable with no further enhancements to the tender specification, at least on plots with favourable orientation.
The build specification, on which contractors were invited to tender, included a contractual requirement to meet the PassivHaus air leakage limit of 0.6h-1 at 50Pa as well as limiting U-values of 0.1W/m2K in the walls, roof and floor, enhanced construction detailing to achieve a SAP y-value <0.05W/m2K and MVHR (mechanical ventilation with heat recovery). With this specification, Code Level 4 is attained without the need for any renewable energy.
The contract was awarded to Lindum Construction in November 2012 who priced competitively at just under £1,400 per sqm for the total cost of the build and proposed to use the Walker Timber Val-U-Therm off-site build system which promised to deliver on the required thermal insulation, quality control and air tightness performance standards which certainly should be inherent in any fabric first approach.
The Val-U-Therm wall system proposed exceeded the thermal insulation requirements with a U-value of 0.09W/m2K which bettered the limit set in the tender specification. This enabled some flexibility in the design for meeting the PassivHaus criteria.
Lindum decided not to use the complete Walker Timber Val-U-Therm system which can include both ground floor and roof elements in one integrated build system. The basis of this decision was cost, as implementing a traditional suspended concrete beam floor and attic truss roof looked likely to be the more cost effective option at the estimating stage. Independent PassivHaus consultants, Encraft, have noted that time and effort would certainly have been saved if the complete Walker Timber Val-U-Therm build-system had been used (PassivHaus Plus magazine, May 2014).
The homes use mechanical heat recovery system and do not have radiators or focal fire; just towel rails in the bathroom and w/c only and a duct heater in the ventilation system, other energy efficient features include triple glazed windows. They are delivering the lowest predicted fuel bills for residents and the lowest whole life costs for emh.
Simon Gregory, MD of Lindum Construction said “We always strive to deliver the best possible quality homes for the families who live in them and best value for money for our clients. This £1.02M project for emh group has been completed within a tight timescale and within budget, achieving a range of building standards including our first accredited PassivHaus homes.”
Miss Raines, one of Hart Lea’s first residents, is delighted with her new home. She said: “I couldn’t have asked for a better house. I am so happy.”
Nigel Simpson, MD of Walker Timber noted: “We were pleased to use our expertise and world-class Val-U-Therm building system to support Lindum Construction in their excellent delivery of the vision and specification required by East Midlands Housing Group”.
Janette Donson – Resident noted, “Energy-wise we have cut the bills to under half …can’t hear the road that’s close by.”