Low Energy Home - Hay Tor

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Energy upgrade of 1950's concrete bungalow. We were trying to achieve the best available insulation (u-values) in all areas and good airtightness within budget restrictions. We are very pleased with the result just over a year after the start of the Retrofit, which makes the home much more comfortable.
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Low Energy Home - Hay Tor : Project images

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CO2 emissionsPrimary energy requirement
Energy target
Retrofit for the Future

Energy and fuel use

Fuel use by type
Primary energy requirement
CO2 emissions

Measured data from renewable generation is not yet available.

Fuel use

Electricity use 2808 kWh/yr 2000 kWh/yr 1995 kWh/yr
Natural gas use13605 kWh/yr 5500 kWh/yr 5684 kWh/yr
Oil use- - -
LPG use- - -
Wood use- - -
Other Fuel - - -
Primary energy requirement 289 kWh/m².yr 144 kWh/m².yr 147 kWh/m².yr
Annual CO₂ emissions 57 kg CO₂/m².yr 29 kg CO₂/m².yr 30 kg CO₂/m².yr
Annual space heat demand 136 kWh/m².yr 50 kWh/m².yr -

Renewable energy

Electricity generationForecastMeasured
Renewables Technology--
Other Renewables Tech--
Electricity consumed by generation --
Primary energy requirement
offset by renewable generation
144 kWh/m².yr 147 kWh/m².yr
Annual CO₂ emissions
offset by renewable generation
29 kg CO₂/m².yr 30 kg CO₂/m².yr

Calculation and targets

Whole house energy calculation method OTHER
Other whole house calculation methodGuestimate, extrapolated from 6 months run with all insulation and airtight measures in place.
Energy target Retrofit for the Future
Other energy targets-
Forecast heating load -


Pre-development air permeability test--
Final air permeability test19 October 20102.05m³/m².hr @ 50 Pascals

Project description

Start date17 May 2010
Occupation date10 December 2010
Location Shrewsbury Shropshire  England
Build typeRefurbishment
Building sectorPrivate Residential
Property typeDetached
Construction typeConcrete frame
Other construction type30mm thick panels fitted into posts at 1.8m centres
Party wall construction
Floor area 78.5
Floor area calculation method Actual Floor Area (SAP)
Building certification

Project Team

OrganisationBest Carpenters
Project lead personClaus Best
Landlord or ClientAlbus - Best
Mechanical & electrical consultant
Energy consultant
Structural engineer
Quantity surveyor
ConsultantAndy Simmonds Simmonds.Mills

Design strategies

Planned occupancyTwo people with mixed day-time use, but at home evenings and weekends.
Space heating strategyHeating with mains gas - Viessmann system boiler with weather compensation feed supplying radiators with TVR's.Wood stove heating the main living area.
Water heating strategySolar hot water - 4m2 flat panels heating 200L insulated tank, with gas condensing boiler as back up.
Fuel strategyMains gas and wood.
Renewable energy strategyNo
Passive Solar strategyEast and west elevations have large windows. On the south elevation the window spaces are reduced due to close proximity of buildings.
Space cooling strategyNatural ventilation during warmer periods plus use of MVHR.
Daylighting strategyI can't give percentages, but the building is a very light home.
Ventilation strategyMVHR all-year round plus openable windows during warmer periods.
Airtightness strategy Airtight membrane fitted to all ceilings in bungalow and taped to walls with grummets for cables and pipes. Tapes fitted to new windows and door frames and plastered over in reveals.A pre-finish air-tightness test achieved 2.05@50Pa. The tester agreed that we would get below 1.5@50Pa at the end of the retrofit project.
Strategy for minimising thermal bridges Due to having fitted internally opening windows we could fit 50mm external wall insulation against the frames of windows and doors.Most of the metal pipes breaking through the building envelope have been converted to plastic ones.
Modelling strategyNo specific modelling strategy, just went for best achievable outcome within budget.
Insulation strategyFitted 100mm Kingspan wallboards to achieve u-value of 0.21 W/m2K.Used polyurethane sprayfoam under felt in the attic to minimise loss of storage space and achieve a u-value of 0.19 W/m2K.Triple glazed windows and doors with u-value of 1.0 W/m2K.
Other relevant retrofit strategies
Contextual information

Building services

Occupancy2 people mixed day time use;
Space heatingwood stove plus gas central heating;
Hot water4m2 solar panels feeding 200l tank plus gas boiler as back up.
VentilationItho Eco 4 MVHR working constantly - 92% effiency;
ControlsMain thermostat, TRV's on radiators, 2 set points for MVHR;
CookingGas hob and electric fan oven
Lightingmostly compact fluorescent with some LED lights;
AppliancesA rated fridge/freezer, dishwasher and washing machine;
Renewable energy generation systemsolar thermal panels;
Strategy for minimising thermal bridgesno fixed strategy for minimising thermal bridges, but tried as best possible within the budget;

Building construction

Volume 197
Thermal fabric area 80
Roof description clay tiles on battens over bitumous felt, 125mm polyurethane foam under felt.
Roof U-value 0.19 W/m² K
Walls description plaster on 75mm medium weight blocks with 125mm filled cavity, external skin consisting of concrete post and panel system with posts at 6' centres,panels are 25mm thick/100mm Kingspan wallboard fixed to external skin with acrylic render;
Walls U-value 0.21 W/m² K
Party walls description None
Party walls U-value -
Floor description Solid concrete floor slab with either parquet floor fitted or 18mm chipboard with carpet.
Floor U-value 0.67 W/m² K
Glazed doors description fully triple glazed back and french doors, half glazed front door
Glazed doors U-value 1.00 W/m² K uninstalled
Opaque doors description
Opaque doors U-value - -
Windows description triple glazed wooden windows
Windows U-value 1.00 W/m² K -
Windows energy transmittance (G-value) -
Windows light transmittance -
Rooflights description
Rooflights light transmittance -
Rooflights U-value -