A Victorian Semi in South Manchester
Street view
A semi-detached house built around 1901 with a near bottom of the class EPC rating from 2011 of F (28); it had solid walls, 25mm of loft insulation, no floor insulation, and single glazed windows. Transforming the house into a low energy home was going to be a retrofit challenge but is now complete.
A new system boiler was added in 2016 by the previous owner leaving the old and barely insulated hot water cylinder. The first challenge was to decide whether to add a new hot water cylinder. The factors were that the orientation of the house was far from optimal for solar thermal and PV, and with much reduced government support financial returns were very long term. The cost of the cylinder was also a factor and a decision was made to swap the boiler with a Vaillant combi with advanced weather compensating vSmart controls.
An assessment followed by Red which gave the house an EPC rating of E (55); the rating had improved with the change of boiler and low energy lighting. Measures included deep wall insulation to the side and rear, new triple glazed windows, secondary glazing to some existing windows, loft and room in the roof insulation, and air tightness measures with a new whole house ventilation system. Our energy advisor called it the best example of a pre-retrofit house that he had seen.
The most recent EPC from June 2019 gives a rating of C (79) with scope for improvement should solar PV be fitted. Reductions of 65% in CO2 and 63% in primary energy use have been achieved along with correspondingly lower energy bills.
Summary of measures
Technical information
Building type
Four bedroom Victorian semi, constructed c1900, extended in 2018
Occupancy
Two people
Measured energy consumption
Estimated from energy bill and in line with recent bills
Electricity - 3,142kWh/a
Gas - 15,415 kWh/a
Modelled energy consumption
From EPC 2019 (181m2)
Space heating - 12,270kWh (68 kWh/m2/a)
Water heating - 2,337kWh
Current primary energy use per m2 - 167 kWh/m2/a
From EPC 2011 (176m2)
Space heating - 44,866kWh (254 kWh/m2/a)
Water heating - 3,332kWh
Energy saving consultants
RED
Green Building Store
Design, architect
Extension - Gibson Architects Ltd
Structural engineer
Extension - Brennan Consult Ltd
Building Regulations Approval
PWC Building Control System Limited
Internal wall insulation
Applied to existing walls after removal of plaster
UdiINRECO wood fibre - 100mm (U=0.35 W/m2K),
UdiIN2CM - 20mm (to return walls)
with Baumit lime plaster finish
Party wall insulation (selected areas)
Knauf Earthwool Flexible Slab - 70-100mm
Windows (sash)
Green Building Store
Performance Sliding Sash (U=1 W/m2K)
Sealed with Orcon F and taped with Contega Solido
Windows (casement)
Lounge and study
GBS Joinery
Custom made with Planitherm Total+ triple glazing (U=0.8 W/m2K), except releaded stained glass toplights with Planitherm Total+ double glazing
Sealed with Orcon F and taped with Contega Solido
Windows (attic roof)
Velfac triple glazed (U=1 W/m2K)
Taped with Contega Solido
Loft insulation
Knauf Earthwool Flexible Slab - 70mm between floor joists
Knauf Earthwool loft roll 44 - 170mm x 2 over
Floors
Lounge and hall floor
Knauf Earthwool loft roll 44 - 170mm between floor joists
Solitex Fronta WA taped with Tescon Vana - to underside
Constivap 2.3 taped with Tescon Vana - over floorboards
Kitchen/Diner floor
Knauf Earthwool loft roll 44 - 170mm
Solitex Fronta WA taped with Tescon Vana - to underside
Room in the Roof insulation
Ceiling (U=0.15W/m2k)
Kingspan K7 50mm between rafters
Kingspan K7 50mm over rafters
Kingspan K118 62.5mm inc 12.5mm plasterboard finish over
Dwarf walls (U=0.15W/m2k)
Kingspan K7 50mm between stud
Kingspan K118 62.5mm inc 12.5mm plasterboard finish over
Attic wall hatches
Fakro DWK combination door (U=1.1 w/m2K)
Extension walls
130mm cavity with 80mm Kingspan K108 cavity board, 37.5mm Kingspan K118 insulated plasterboard (U=0.15W/m2k)
Extension roof
145mm Kingspan Thermaroof TR27 (U=0.15W/m2k)
Extension floor
120mm Kingspan K103 floorboard between joists with 25mm perimeter insulation (U=0.14W/m2k)
Windows (extension)
IdealCombi Futura+ triple glazed (U=0.87 W/m2K)
Taped with Contega Solido
Windows (extension roof)
Fakro DMF and DXF triple glazed (U=0.88 W/m2K)
Taped with Contega Solido
Air tightness (Air permeability)
Measured mid works - Waxwing Energy - 10.6 m3/m2/h @50Pa
Measured after works - Green Footsteps Limited - 6.24 m3/m2/h @50Pa (UK standard for Part L) but serious air losses since sealed up
Boiler
Vaillant ecoTEC plus 38 combination boiler (A rated for heat and water, 94% ErP efficiency, 89.3% SEDBUK rating) with vSMART heating controls incorporating weather compensator
MVHR
Design by Green Building Store
Paul Novus 300 unit (over 93% heat recovery rate efficiency), with Lindab ducting
Based on 177m2 floor area/466.26m3 actual floor volume/423.96m3 PHPP floor volume)
Installation by Airtight Build Ltd
edited 28 April 2021
Images
A new system boiler was added in 2016 by the previous owner leaving the old and barely insulated hot water cylinder. The first challenge was to decide whether to add a new hot water cylinder. The factors were that the orientation of the house was far from optimal for solar thermal and PV, and with much reduced government support financial returns were very long term. The cost of the cylinder was also a factor and a decision was made to swap the boiler with a Vaillant combi with advanced weather compensating vSmart controls.
An assessment followed by Red which gave the house an EPC rating of E (55); the rating had improved with the change of boiler and low energy lighting. Measures included deep wall insulation to the side and rear, new triple glazed windows, secondary glazing to some existing windows, loft and room in the roof insulation, and air tightness measures with a new whole house ventilation system. Our energy advisor called it the best example of a pre-retrofit house that he had seen.
The most recent EPC from June 2019 gives a rating of C (79) with scope for improvement should solar PV be fitted. Reductions of 65% in CO2 and 63% in primary energy use have been achieved along with correspondingly lower energy bills.
Summary of measures
- The sash windows to the first and second floors were replaced by new triple glazed sash windows from Green Building Store.
- Two new triple glazed Velux roof windows were installed, one over the stairs, the other in the 2nd floor ensuite.
- A replacement bay window was fitted in the front living room, with the stained glass releaded and set behind double glazed units; the fixed and opening casements are triple glazed. A replacement triple glazed window with a 'Manchester' roof light was fitted at the side of the house. In the front door the stained glass panels were backed by laminated glass reducing draughts and improving security.
- Insulation was added with air tightness measures: Phenolic insulation to the room in the roof for the roof and eaves; 100mm of Udi IN RECO wood fibre internal wall insulation to external walls, with 25mm of Udi 2INCM to return walls finished with lime plaster; 170mm of mineral wool under the floor of the lounge and hall; 410mm of mineral wool was fitted in the attic floors.
- Radiators were replaced with smaller, more efficient models with TRVs.
- An MVHR whole house ventilation system with a Paul Novus 300 unit designed by Green Building Store was installed after exploring options including MEV. In the end MVHR offered a more complete solution. An air tightness test was undertaken mid-retrofit, giving a figure of 11 air changes per hour (air permeability test). This was improved post-retrofit (in August 2018) to 6 air changes per hour, high for an MVHR system. However since then several major sources of air penetration were found and dealt with and a further informal air test demonstrated how a much lower figure would be expected.
- A small extension to the rear designed by Gibson Architects was built creating a new kitchen/diner from the rear living space; the space occupied by the old kitchen was converted to provide a study, cloakroom and WC. The extension incorporates IdealCombi terrace doors and windows, Fakro roof windows, and new walls and ceilings with low U-values. The garden was landscaped to link the extension with the garden.
- The rear attic was boarded and the ceiling lined with a reflective membrane to reduce heat gain and dirt from the slate roof.
- Further measures focusing on the basement may be pursued in future. The floor in one of the rooms has been renewed and improved, but still minimal, insulation has been added. Gaps in the building fabric were sealed.
- The feasibility of changing the gas boiler to a heat pump has been examined. With a peak heat loss of c7kW this is feasible and despite current low gas prices running costs would be broadly similar to the current system. However there are a number of factors against: the boiler is relatively new, the current radiators aren’t optimised for low temperature, and the cost of the new system is high even with likely RHI payments.
Technical information
Building type
Four bedroom Victorian semi, constructed c1900, extended in 2018
Occupancy
Two people
Measured energy consumption
Estimated from energy bill and in line with recent bills
Electricity - 3,142kWh/a
Gas - 15,415 kWh/a
Modelled energy consumption
From EPC 2019 (181m2)
Space heating - 12,270kWh (68 kWh/m2/a)
Water heating - 2,337kWh
Current primary energy use per m2 - 167 kWh/m2/a
From EPC 2011 (176m2)
Space heating - 44,866kWh (254 kWh/m2/a)
Water heating - 3,332kWh
Energy saving consultants
RED
Green Building Store
Design, architect
Extension - Gibson Architects Ltd
Structural engineer
Extension - Brennan Consult Ltd
Building Regulations Approval
PWC Building Control System Limited
Internal wall insulation
Applied to existing walls after removal of plaster
UdiINRECO wood fibre - 100mm (U=0.35 W/m2K),
UdiIN2CM - 20mm (to return walls)
with Baumit lime plaster finish
Party wall insulation (selected areas)
Knauf Earthwool Flexible Slab - 70-100mm
Windows (sash)
Green Building Store
Performance Sliding Sash (U=1 W/m2K)
Sealed with Orcon F and taped with Contega Solido
Windows (casement)
Lounge and study
GBS Joinery
Custom made with Planitherm Total+ triple glazing (U=0.8 W/m2K), except releaded stained glass toplights with Planitherm Total+ double glazing
Sealed with Orcon F and taped with Contega Solido
Windows (attic roof)
Velfac triple glazed (U=1 W/m2K)
Taped with Contega Solido
Loft insulation
Knauf Earthwool Flexible Slab - 70mm between floor joists
Knauf Earthwool loft roll 44 - 170mm x 2 over
Floors
Lounge and hall floor
Knauf Earthwool loft roll 44 - 170mm between floor joists
Solitex Fronta WA taped with Tescon Vana - to underside
Constivap 2.3 taped with Tescon Vana - over floorboards
Kitchen/Diner floor
Knauf Earthwool loft roll 44 - 170mm
Solitex Fronta WA taped with Tescon Vana - to underside
Room in the Roof insulation
Ceiling (U=0.15W/m2k)
Kingspan K7 50mm between rafters
Kingspan K7 50mm over rafters
Kingspan K118 62.5mm inc 12.5mm plasterboard finish over
Dwarf walls (U=0.15W/m2k)
Kingspan K7 50mm between stud
Kingspan K118 62.5mm inc 12.5mm plasterboard finish over
Attic wall hatches
Fakro DWK combination door (U=1.1 w/m2K)
Extension walls
130mm cavity with 80mm Kingspan K108 cavity board, 37.5mm Kingspan K118 insulated plasterboard (U=0.15W/m2k)
Extension roof
145mm Kingspan Thermaroof TR27 (U=0.15W/m2k)
Extension floor
120mm Kingspan K103 floorboard between joists with 25mm perimeter insulation (U=0.14W/m2k)
Windows (extension)
IdealCombi Futura+ triple glazed (U=0.87 W/m2K)
Taped with Contega Solido
Windows (extension roof)
Fakro DMF and DXF triple glazed (U=0.88 W/m2K)
Taped with Contega Solido
Air tightness (Air permeability)
Measured mid works - Waxwing Energy - 10.6 m3/m2/h @50Pa
Measured after works - Green Footsteps Limited - 6.24 m3/m2/h @50Pa (UK standard for Part L) but serious air losses since sealed up
Boiler
Vaillant ecoTEC plus 38 combination boiler (A rated for heat and water, 94% ErP efficiency, 89.3% SEDBUK rating) with vSMART heating controls incorporating weather compensator
MVHR
Design by Green Building Store
Paul Novus 300 unit (over 93% heat recovery rate efficiency), with Lindab ducting
Based on 177m2 floor area/466.26m3 actual floor volume/423.96m3 PHPP floor volume)
Installation by Airtight Build Ltd
edited 28 April 2021
Images
The original water tank just under the uninsulated and unlined slate roof
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Bringing in the new triple glazed sash windows
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Installing the new sash windows
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New bay window with releaded stained glass. The internal wall insulation is shown before treatment to surrounds and plastering
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The 'room in the roof'/ Bedroom 4 after the ceiling was removed and before 150mm of insulation was added
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Loft insulation, 1960s style?, 25mm deep
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Pipework routes in attic after 'thinning out' redundant pipework - showing scope for sealing up for air tightness
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170mm of insulation, and membrane under the hall floor, sealed at the edges
Rear extension
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