Lang Lane Low energy house - How it's done
Posted by Christopher Hirst on
No. 9 Lang Lane West Kirby
A passive house designed by John McCall Architects, which runs on the energy equivalent to that used by a 40W lightbulb, has won a national green award.
Practice director, Colin Usher, designed the home in Lane Lane, West Kirby for himself and his wife.
It won the Domestic Newbuild category of the Buildings and Energy Efficiency Awards.
It was carefully orientated so the windows and solar roof panels get optimum sunlight exposure.
The result is a house that has been lived in for a number of years and the energy cost for heating, lighting, hot water and cooking is just £15 per annum.
To construct such a building, precision of build becomes paramount, for this reason it is important to use materials which are manufactured to a tolerance which facilitates such a build system. Thermally efficient Hooga blocks in conjunction with the Hooga mortar system meet these criteria and consequently were used to construct the load bearing external walls of this house. This allowed the thickness of the external walls to be reduced to just 150mm. The addition of a 200mm Brillux Externally Insulated Thermally Composite System (ETICS) means the external walls of this house have a U-Value of 0.12W/m2K with an overall thickness of only 350mm.
“This is a simple building and in effect, runs on the same amount of power used by a 40W light bulb”
Colin Usher
Practice Director
John McCall Architects
Hooga thermal blocks for this build only weigh 60Kg/M2, resulting in a lightweight external wall system which sits on an insulated Hooga foundation, consisting of 250mm of load bearing insulation on top of which is a structural concrete raft – with a total U-value 0.11W/m2K. When designing with such high levels of insulation it is important that the junctions of the building envelope are either thermal bridge free or any thermal bridge is modelled to minimise any possible heat loss. The Hooga foundation and Hooga wall system use a Passive House approved junction which is a thermal bridge free junction.
Thermal mass is an important element which enables this building to perform as designed. The external walls, intermediate floors and internal partitions are all constructed of high mass concrete materials. The large thermal mass of the building helps to maintain an even temperature in winter and summer. For example once primed (up to living temperature) the building will lose less than 10C per day even on the coldest winter’s day even with no additional heating.
The thermal block system is in effect airtight for the purposes of the air test but is still breathable. The inherent airtightness of the Hooga system allows the builder to concentrate on the junctions of the building, for example the junction of the wall to window. The use of specialist tapes and seals were used to ensure an airtight seal at these junctions, in addition all personnel on site are educated to be aware of the affect of their actions on the airtight membrane and to understand what the airtight membrane actually is and how their actions within the building could impact on the airtight layer.
All appliances in the property are A+ rated or better, lights are naturally low energy and when combined with the air source heat pump mean that the house has a total energy use of just 20kWh /M2/year. Due to the super insulated envelope and the low air permeability the energy required for heating is extremely low. Normally water is heated up to in excess of 800C in a traditional heating system, however, in this house the underfloor heating only requires a water temperature of around 350C allowing the air source heat pump to work efficiently at a COP of 3.
To maintain a thermally efficient envelope the windows must be of the highest quality, for this reason triple glazed aluminium faced wooden windows were installed. The window and door system used has a Ug value of 0.5W/mK and incorporate a three seal system which ensured that the integrity of both the thermal and airtight layers remain intact.
Chris Hirst