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Transform your house into a low carbon, sustainable home
KNOWLEDGE BANK

Air Source heat pump (ASHP)

An air source heat pump absorbs heat from the outside air (even when the weather is cold) to heat your home and water.
It uses electricity to run, but the heat output can be around four times the electricity input.

MAIN BENEFITS:
• Significantly reduces the carbon emissions from heating your home, to near-zero if run on electricity from a renewable source.
• Almost any home is or can be made suitable for an air source heat pump.
• Should last around 20 years, with less maintenance than an average gas boiler.

THINGS TO CONSIDER:
• Underfloor heating or large radiators, and a hot water tank, are needed.
• To get the most out of a heat pump, it’s best combined with a well-insulated home.
• The noise of an air source heat pump is often compared to a tumbler dryer.

OPTIONS:
Getting the right size of heat pump is critical, and a heat survey is needed to determine this. Having larger radiators running at a lower temperature means you can have a more efficient heat pump.

Ground source heat pump (GSHP)

A ground source heat pump absorbs heat from the ground (even when the ground feels cold) to heat your home and water. It uses electricity to run, but the heat output can be around four times the electricity input.
A ground source heat pump absorbs heat from the ground (even when the ground feels cold) to heat your home and water. It uses electricity to run, but the heat output can be around four times the electricity input.

MAIN BENEFITS:
• Significantly reduces the carbon emissions from heating your home, to near-zero if run on electricity from a renewable source.
• The ground retains heat from the summer, which a GSHP draws on when the weather is coldest.
• Has a long lifespan: 50 – 100 years for ground components and up to 25 years for indoor components.

THINGS TO CONSIDER:
• Only possible where there is considerable outside space, and substantial works to install the pipework in the ground is required.
• Underfloor heating or large radiators, and a hot water tank, are needed.
• To get the most out of a heat pump, it’s best combined with a well-insulated home.

OPTIONS:
The piping system can be laid vertically or horizontally.
• Vertical piping goes 100 – 150 meters deep depending on what the ground is like. This is more expensive than horizontal piping.
• Horizontal piping goes 1-2 meters deep but requires a bigger area, between 300 and 700m2.

External wall insulation (EWI)

External wall insulation (EWI) can be used on the outside of homes with solid walls. It means you lose less heat through your walls.
MAIN BENEFITS:
• Reduces heat loss through the walls of your home, meaning that your heating system can be smaller and cheaper to run.
• Can be used at a greater thickness than internal wall insulation, reducing heat loss further.
• Will retain the ‘thermal mass’ of the building, reducing the effect of temperature changes throughout the day, and so maintaining a more comfortable temperature in your home.
• Provides a new façade, which for some people will be a chance to refresh the look of the house.

THINGS TO CONSIDER:
• Changes the appearance of the house: there are a variety of finishes available.
• Planning permission may be needed, and in some cases may not be given, for example for period properties or in conservation areas.
• Needs to be designed to avoid condensation and heat loss through ‘thermal bridging’.

OPTIONS:
There are many finishes available. For example, renders in any colour, brick slips, tiles, timber cladding and decorative boards.

Depending on the construction of the building, different materials may be used for the insulation layer. For example, mineral wool, woodfibre, cork or expanded polystyrene.

Internal wall insulation (IWI)

Internal wall insulation (IWI) can be used in homes with solid walls. It means you lose less heat through your walls.
MAIN BENEFITS:
• Reduces heat loss through the walls of your home, meaning that your heating system can be smaller and cheaper to run.
• Can be used if you don’t want to change the appearance of your house.
• Planning permission isn’t required even in conservation areas. (Though listed buildings may need listed building consent.)

THINGS TO CONSIDER:
• Reduces the area of rooms by about 40-110mm, along just the walls with an external face.
• Disruptive to install, because skirting, radiators, and electrical sockets need to be re-fitted. But can be installed one room at a time, or done when other renovation is being carried out.
• Needs to be designed to avoid condensation and heat loss through ‘thermal bridging’.

OPTIONS:
Depending on the construction of the building, different materials may be used for the insulation layer (hidden by the wall finish). For example, rigid foam boards, mineral wool, wood fibre, or cork.

Cavity wall insulation (CWI)

Cavity wall insulation (CWI) can be used in homes with cavity walls (the external walls of the house have a gap between two leaves of brickwork). It means you lose less heat through your walls.

MAIN BENEFITS:
• Reduces heat loss through the walls of your home meaning that your heating system can be smaller and cheaper to run.
• Minimal disruption to install.
• Will retain the ‘thermal mass’ of the building, reducing the effect of temperature changes throughout the day, and so maintaining a more comfortable temperature in your home.
• The cost of installing CWI is usually covered by lower bills within around 5 years.

THINGS TO CONSIDER:
• A borehole survey should be completed before filling cavity walls, to ensure suitability.
• The materials used for CWI should be chosen based on the depth of cavity and location of the building, avoiding fibrous materials that will absorb moisture and can slump over time reducing the insulative qualities of the wall.

Loft insulation

Insulation that can be rolled out in your loft (between and above ceiling joists) to reduce the amount of heat lost through the ceiling.

Main benefits:
• Reduces heat loss through the ceiling.
• The cost of installing loft insulation is usually covered by lower bills within 2 to 3 years.

Things to consider:
• Loft hatches should also be insulated and draught-proofed.
•Loft vent trays should be installed for good ventilation.

Underfloor insulation (UFI)

Insulation that can be fitted under suspended timber or solid floors to reduce the amount of heat lost through the floor.

MAIN BENEFITS:
• Reduces heat loss through the floor.
• Significantly reduces draughts coming up through suspended timber floors.
• Makes the floor warmer to sit and walk on.
• Can be incorporated with underfloor heating.

THINGS TO CONSIDER:
• In houses with solid floors, the floors may need to be raised slightly, impacting the skirting boards and doors.
• In suspended timber floors, the installer needs to take care around the ends of joists to ensure that they don’t attract moisture (by being colder than before).
• In either solid floors or suspended timber floors, the installer needs to take care around the junctions with the wall insulation to ensure a robust retrofit and minimise thermal bridges.

Windows and doors

Replacing single glazing or old double glazing with new double or triple glazed windows and doors can reduce heat loss and draughts.

MAIN BENEFITS:
• Reduces heat loss through windows and doors.
• Can reduce draughts.
• Can improve the appearance of windows and doors.

THINGS TO CONSIDER:
• Changes the appearance of windows and doors, including the look of the glass.
• If considering solid wall insulation, it is best done at the same time. This means the installations can be designed to minimise heat loss through ‘thermal bridging’, and it is likely that it will also costs you less overall.
• Planning permission may be required, and in some cases may not be given, for example for period properties or in conservation areas.

Ventilation, required when insulating

We generate a lot of moisture in the home through cooking, washing and breathing. This moisture often escapes through gaps and cracks around the home (draughts).

WHY IS VENTILATION NEEDED?
We generate a lot of moisture in the home through cooking, washing and breathing. This moisture often escapes through gaps and cracks around the home (draughts). This uncontrolled ventilation is significantly reduced when insulating, meaning that controlled ventilation is needed. A well designed ventilation system will monitor and remove excess moisture from the home to ensure good internal air quality and reduce the chances of condensation and mould.

WHAT IS A VENTILATION SYSTEM?
Air is extracted from the bathroom/s and kitchen/s using extractor fans. The most common form of extractor fans are those that come on when the bathroom light is turned on. Dedicated air-inlets will be in the bedrooms, lounges, etc. to allow air into the home to replace the extracted air. The most common form of air inlets are ‘trickle vents’ in windows (small adjustable slits in the frame of the window), though a different type of inlet might be necessary or more desirable.

THINGS TO CONSIDER:
• Ventilation should be installed before or concurrently with any wall insulation, to remove the need to pierce the newly installed wall insulation, which could potentially lead to draughts.
• If there are open fireplaces in the home any combustion ventilation requirements should be taken into account.

CASE STUDIES

Flat in mansion block, Clapham
Flat in mansion block, Clapham

When Andy and Agi did up their top floor flat they wanted to solve the draughts, damp and condensation problems. read more

Victorian house, <br>Peckham
Victorian house,
Peckham

This case study is about putting your money where your mouth is: Chris is a director of Parity Projects, and has helped to set up Ecofurb. read more

VICTORIAN TERRACED HOUSE, BATTERSEA
VICTORIAN TERRACED HOUSE, BATTERSEA

JP and Gabi had been living in their house for seven years when they got the opportunity to renovate after their wedding. read more