Architect's Notes for 2a Bramcote Drive
Built between 2021-23 this new-build was conceived as a *PassivHaus and replaces an outdated 1960s bungalow. After investigating the options for retaining, enlarging and retrofitting it was decided that the project held more potential as a demolition and replacement project in terms of buildability, performance and flexibility.
While there is an additional upfront carbon impact to demolition and replacement, we reasoned that employing the lowest impact construction methods and the additional energy efficiency achievable on a new-build would go some way to mitigating this while potentially making the project more affordable.
PassivHaus modelling was carried out to determine insulation thickness, glazing design suitability and crucially, assess the overheating potential. Too much glass increases both overheating and heat loss and in turn can require more insulation and external shading. Keen to have a relatively large amount of glass on the southwest gable we identified the need for a sizeable retractable awning. We also included an increased roof overhang along the longer southeast facing front elevation to offer some shade to the upper-level windows and an entrance canopy to shade the front door. PassivHaus is as much about comfort and good air quality as it is about energy efficiency.
It was also important to choose build methods and materials that minimise upfront carbon impacts so as to offset the demolition impacts. The walls are engineered deep timber frame i-joists* with cellulose based insulation. Walls have 400 mm cellulose between the i-joists and an additional 50 mm layer of mineral wool in the service void. Roofs have 450 mm cellulose and 50 mm mineral wool in the service void. The insulated raft has 300 mm thick polystyrene underneath and 150 mm thick edge upstands.
*strong, lightweight, "I" shaped engineered wood joist.
While there is an additional upfront carbon impact to demolition and replacement, we reasoned that employing the lowest impact construction methods and the additional energy efficiency achievable on a new-build would go some way to mitigating this while potentially making the project more affordable.
PassivHaus modelling was carried out to determine insulation thickness, glazing design suitability and crucially, assess the overheating potential. Too much glass increases both overheating and heat loss and in turn can require more insulation and external shading. Keen to have a relatively large amount of glass on the southwest gable we identified the need for a sizeable retractable awning. We also included an increased roof overhang along the longer southeast facing front elevation to offer some shade to the upper-level windows and an entrance canopy to shade the front door. PassivHaus is as much about comfort and good air quality as it is about energy efficiency.
It was also important to choose build methods and materials that minimise upfront carbon impacts so as to offset the demolition impacts. The walls are engineered deep timber frame i-joists* with cellulose based insulation. Walls have 400 mm cellulose between the i-joists and an additional 50 mm layer of mineral wool in the service void. Roofs have 450 mm cellulose and 50 mm mineral wool in the service void. The insulated raft has 300 mm thick polystyrene underneath and 150 mm thick edge upstands.
*strong, lightweight, "I" shaped engineered wood joist.
PassivHaus
“Buildings are a significant culprit of carbon emissions – accountable for 35% of total global energy consumption. Backed with over 30 years of international evidence, Passivhaus is a tried & tested solution that gives us a range of proven approaches to deliver net-zero-ready new and existing buildings optimised for a decarbonised grid and augmented for occupant health and wellbeing. Passivhaus buildings provide a high level of occupant comfort using very little energy for heating and cooling.
Passivhaus adopts a whole-building approach with clear, measured targets, focused on high-quality construction, certified through an exacting quality assurance process”.
passivhaustrust.org.uk
“Buildings are a significant culprit of carbon emissions – accountable for 35% of total global energy consumption. Backed with over 30 years of international evidence, Passivhaus is a tried & tested solution that gives us a range of proven approaches to deliver net-zero-ready new and existing buildings optimised for a decarbonised grid and augmented for occupant health and wellbeing. Passivhaus buildings provide a high level of occupant comfort using very little energy for heating and cooling.
Passivhaus adopts a whole-building approach with clear, measured targets, focused on high-quality construction, certified through an exacting quality assurance process”.
passivhaustrust.org.uk
