Green Network for Social Housing

The Dormont Passivhaus Development consists of 8 semi-detached, 2-bedroom and 3-bedroom, homes built to Passivhaus-standard.

Passivhaus is a performance-based set of design criteria for creating very low energy, low-carbon homes, which use around 90% less energy than comparable standard built homes and deliver high levels of internal air quality and thermal comfort for occupiers. Each home in the Dormont Passivhaus Development was designed by David J. Major of White Hill Design Studio using the Passivhaus principles in mind:

• maximising the use of insulation 

• inclusion of energy efficient windows 

• designing in, strict airtightness specifications • minimum energy demand for space heating & cooling    

• minimum primary energy use for all appliances               

• optimising passive solar gain• optimising other incidental heat gains using a mechanical ventilation & heat recovery unit

Walls: The external fabric for each home was produced using prefabricated 260mm wide ‘SpaceStud’ frame construction faced on both sides with 9mm OSB with each void filled with mineral fibre insulation and an additional layer of 70mm rigid insulation board on the inner face finished with plasterboard. 

Roof: The roof areas were constructed using 300mm deep engineered joists sheathed both sides with 9mm OSB and fully filled with mineral fibre insulation with an additional layer of 55mm rigid insulation board on the inner face finished with plasterboard. 

Floor: To minimise heat loss, the ground floor’s concrete slab was covered with 22mm chipboard on 200mm rigid insulation. 

Internal Heat Demand: The designed air tightness allows the installed Mechanical Ventilation and Heat Recovery (MVHR) units to perform at 90% efficiency. The 2-bedroom homes use the ‘Paul’ Focus (F) 200 unit whilst the ‘Paul’ Novus (F) 300 unit is used in the 3-bedroom homes. Each unit maintains a constant temperature within the home, by bringing fresh air from outside into the home and balancing its temperature using the heat energy from stale out-going air from within the home.

Domestic Hot Water:  The combined Worcester Bosch Greenskies roof mounted solar thermal panels produce the home’s hot water requirement during the warmer, sunnier months, whilst the Woodfire F12 10.8 kW biomass log stove produces the hot water during the colder, darker months.  The Woodfire F12 stove was chosen as it draws the combustion air directly from outside the home and delivers 90% of the heat generated to the hot water. 

Feedback

Overall tenant satisfaction has been high, “This is a dream come true” said one tenant after she had moved in.  Others have said “Brilliant, peaceful, a lovely house in lovely scenery”; “Why has it taken so long to build projects like these”; “It feels just like home – it feels so right”; “The house is very warm and very beautiful. We’re so lucky to have landed here.”

Jamie Carruthers, manager of the Dormont Estate, is pleased with the eight Passivhaus homes: “Huge energy savings are being noticed by the tenants in excess £1,000 per year. The MVHR systems running costs are minimal and on-going monitoring should give its actual running costs and help identify how this cost can be further reduced.”

The 2 bedroom homes have average annual energy bill of £400 whilst the 3 bedroom homes are witnessing energy bills of just £550 per year.  Each household pays an additional £100 or so per year for firewood to heat their hot water requirements during winter, some of which is sourced from timber grown sustainably on the estate.

Top Tip

Jamie concludes: “The correct contractor is important. CCG (Scotland) Ltd as the contractor was the correct choice for this build.  They have continued to progress their knowledge of Passivhaus from the lessons learned during this development.”