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Low energy refurbishment: Where do we start?

Question: We have a detached three bedroomed house here in Leeds, which we think was built in the 1920s. It has only small cavity walls at the corners. A two storey kitchen/bedroom extension was been built onto the back of the house over twenty years ago. We have had sheepswool added to the rockwool insulation in the loft space so that we have about 14 inches of insulation there now.

Our solar thermal panel is now working but we have had several problems with it and it has turned out to be an expensive investment. This has made us wary and a little frightened of embarking on what ought to be a sensible changes to our house. We decided when it was put in to have the solar thermal system linked to our radiators and our combi-boiler. This was I think a mistake. In the winter the combi-boiler heats the water which then goes up to the heat store cylinder in the loft space; overnight the temperature in the heat store drops precipitously. During the night the noise of the combi-boiler working somethimes prevents me from sleeping.

We are a retired couple and think that it would be sensible to have a toilet and walk in shower downstairs, as well as a more comfortable ambient temperature in the house. The toilet and shower would need to be in an extension built onto the house.


a) How can we best improve the energy efficiency of our house and have a comfortable ambient temperature especially in the winter?
b) Together with a new toilet and shower extension, what kind of ball park figure cost is this likely to be.
c) Would the investment be just that, or would any of this be cost effective?
d) How and where do we set about getting reliable advice as to what to do?
e) Is planning permission needed? Are there standards for any insulation work that is carried out?
f) How much disruption would there be?

Answer: Thanks for your question, it is very pertinent to many of the problems people are experiencing in existing housing

Fabric first

Green Building Store’s philosophy is very much to focus on fabric first as the most cost effective option for reducing CO2 emissions from homes. Focusing on the building fabric can be more difficult and daunting than adding bolt-on renewable to a house but is, in our opinion, much more effective (and cost-effective). It also has the advantage of making your home cosier and warmer!

Insulation measures tackle the fabric in your house we would suggest the following:

1) Improving airtightness and draught-proofing (dealt with in another Green DIY section: Insulating hard-to-treat homes)

2) Insulation measures

a) Cavity wall insulation would be a good first port of call. Given the era of your property, you will need to ask installers to inspect the cavity (using a small keyhole camera) to see whether cavity wall insulation is suitable – the cavity may not be suitable for filling if the wrong wall ties are used or if there are no cavity wall trays etc
b) Loft insulation – sounds like you have plenty of insulation in the loft – well done!
c) Insulating floors – see our separate Green DIY advice on Insulating suspended timber floors & Insulating solid floors.
d) External insulation – for exterior of the house. Your house might be suitable for this – which could then be finished with either render or brick slips. External insulation can offer great benefits – like wrapping the house in a giant teacosy – helping to minimise thermal bridges and also potentially helping with airtightness issues. External insulation also has the advantage of being less disruptive than internal wall insulation measures, although is not always completely straightforward as to work best the insulation needs to go down to the foundations and ‘services’ such as drains etc might need to be moved
e) Internal insulation – if external insulation is not possible (as is the case with many listed buildings or stone buildings) then you could get internal insulation applied to the inside of all exterior walls. This can obviously be disruptive and reduces internal space, but it can be done on a room by room basis ( eg when decorating takes place). Internal insulation is less good than external in reducing thermal bridging but still makes a positive contribution. See our advice on Internal Wall Insulation.
f) Triple glazed windows to finish off any eco refurbishment it is important to have windows with high thermal performance to help keep the heat in.

Information on Passivhaus refurbishments

New extension

We would suggest that you get an architect to help you design this as you will almost certainly need planning permission for this. We would suggest that you look at the AECB website to see if there are any architects in your area. It makes sense to build the extension to as high a standard as you can, even if you can’t do the rest of the house at the moment. In an ideal world, we would suggest that the extension be built using Passivhaus principles and requirements, because the rest of the house will hopefully someday catch up.

The extension will have to be built to new Building Regulations but at the moment there is no UK Government endorsed standard for refurbishment. As a rule of thumb, you should expect to pay between £1-2K per m2 for newbuild, partcularly for a small extension with a bathroom or kitchen.

Whole house strategy

We believe that when people do try to undertake an energy efficient refurbishment of their homes, they first develop a ‘whole house plan’ of all the measures that they would like to implement. Even if funds are not sufficient to do the whole refurbishment, the ‘whole house’ plan will still offer a coherent approach to any piece-meal measures undertaken. For this reason, we always recommend use of triple glazing in windows and doors, because eventually the rest of the house will need to catch up…

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