How do you insulate a loft conversion?

With all the demands on space and the value of homes rising rapidly, loft conversions are becoming a great way to expand the floor space of your home and increase its value. As you might know, the roof is one of the key places where heat is lost in the home, so ensuring it is very well insulated is absolutely essential. Here we will discuss what you can do if you have a roof room and need insulation, and how this can complicate the matter!

Roof room building regulations

Over the years, building regulations have become ever more strict; this has meant that roof rooms converted more than 10 years ago are unlikely to meet current standards. Furthermore, the standards prior to 2003 were actually fairly poor and chances are that if your conversion was done some time ago, there is very little insulation installed.

Currently, building regulations for loft conversions dictate that the u-value of the roof must be 0.18W/m2 or lower. This equates to a thick 270mm layer of fibre or wool insulation, about 175mm of rigid board insulation or around 125mm of high performance spray foam. If you are getting a loft converted now, your builder should be installing at least up to these standards.

Further, if you have a roof room and are looking to re-roof, you must ensure that the new building regulations of 0.18W/m2 are followed. Fortunately, insulation can usually be added externally, between the roof room ceiling and the new roof, during the process of re-roofing.

Should I retrofit insulation?

Insulating a standard loft is really straightforward and will save you a lot on your energy bills. Unfortunately, to insulate a loft conversion, which needs to be retrofitted, can be really expensive and it may not be viable for other practical reasons.

There are 3 areas that we can identify that will need insulating to ensure your house is up to standard:

  1. The residual loft space – This is the joist area that does not form part of the roof room. Often it is used as a storage area and is easily accessible. You can insulate this area in the same way to would insulate a standard loft – by laying wool insulation between the joists. This is cheap and straight forward.
  2. The stud walls – These are the small walls at the end of the sloping ceiling. You can insulate these by stapling wool insulation or adding rigid boards. Again this is relatively straight forward and inexpensive.
  3. The sloping roof – This is usually the largest area of the roof room and unfortunately the most difficult to insulate. This will be an expensive job whatever the approach and is unlikely to pay back very quickly.

So the first thing you should do is try to insulate the easy to reach places like the residual space and the stud wall. You can potentially DIY this and it will pay back very quickly.

Insulating the sloping roof internally or externally?

If you do wish to insulate the sloping roof there are two ways you can go about it. One way is to insulate between the ceiling and the roof – which can be done by either taking down the ceiling or taking the tiles off the property (re-roofing). So if you are in the process of re-roofing, it makes sense to get the insulation done, otherwise this will be cost prohibitive.

The other, cheaper option would be to insulate internally, by adding another layer to the ceiling. This is effectively a stud wall with insulation between. This option is often not practical because it restricts the height of the room in a space that is usually already somewhat restricted.

So roof room insulation is great if you have it, but retrofitting it is clearly costly and impractical for many. If it is not something you will be able to do in the near future, do ensure that the easy to insulate areas we have discussed are insulated and you have made all those low cost savings you can.

Installing loft insulation

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