Insulating a bedroom

[Fred]

Hi,

The front bedroom of our house is noticeable colder than the back bedroom. I used to think this was because the rear of the house caught the sun but we haven't had sun for some weeks so there must be more to it than that.

The rear of the house (1970s) is brick with an insulated cavity and breeze block inside. The front of the house is (I guess) breeze block inside and then tiled cladding. Does the cladding do anything with respect to trapping heat? Surely it is not airtight so in effect, don't we have a single skin wall on the front of the house?

I think the best solution would be to remove the cladding and put kingspan on the front of the house and then put the tiles (or something prettier! - but what?) on top. However this might also be expensive because I wouldn't be DIYing that.

I was wondering whether a good compromise would be to put kingspan on the inside and plasterboard over that, at the expense of losing an inch or two from the room's length? Can't you even get combined sheets that are plasterboard pre-bonded to the insulation?

I'm not too good with u-values; what would be the best thickness of kingspan to use?

The room has a big radiator but that only helps when the heating is on. Is it worth running the front of the house on a separate zone to the rear of the house?

TIA

[safety]

Dear TIA The insulation needs to be "joined up" ... you have a bit of a problem here it would help if you were to have stated if the house is terraced, detachted or semi If it is terraced then it is probably worth insulating the whole of the front but not unless you DIY as to have it done professionally you will be dead before the pay back if ever If it is detached then I would consider the internal route and if you cannot diy the outside then go internally I have done this with success in the past using 2" Kingspan attached with plaster board glue to the walls supplemented by the plastic and stainless steel 6" fixings for external Kingspan, followed by 3/8" plaster board similarly (but with staggered fixings) fixed and then skimmed with finish It means taking off all architraves, skirtings etc and putting them back on with special plaster board fixings it means loss of 2.5" inside but hell it is really warm and worth while

Chris

[deano]

Hi Fred.

Before you do anything further, it would be worth speaking to your local council regarding advice for insulating your property. Not sure which dept takes care of these issues but there are grants available for certain types of property to improve energy efficiency... they would likely be able to send someone round to you to assess the situation and, even if you did not qualify for a grant, they would definitely be able to help you, based on their experience with similar properties in the area.

I've done a couple of jobs of this nature, here in Potters Bar, which usually involves battening out the walls, friction fitting slabs of Kingspan in between, covering with a vapour barrier and then tacking up foil-backed wall board. Also retro-fitting trickle vents to pvc window frames and installing de-humidifier fans and air bricks where necessary... this is of course where condensation has been evident, but you will also have a dew point going on somewhere, in your property where the warm is meeting the cold!

HTH

deano.

[js.b1]

Solar gain is worth 4oC by 10:30am where one room is South facing w/ bay windows, another North facing. After the sun has gone it goes into reverse (-1oC difference).

Batten the walls. Friction fit 25-40-50mm celotex between the battens. Cover with 25mm celotex to remove cold bridging. Fit plasterboard over the top (or Marmox which has higher insulation but vastly higher cost if you are desperate to squeeze in every last millimetre as being insulatory). Thin 3mm skim with finishing plaster.

If the wall is solid, SBR the wall, then cement slurry for waterproofing (Mapei keraflex which is a cementitious adhesive to making your own cement slurry with SBR). SBR is obtainable from B&Q, Screwfix and online suppliers - a waterproof version of PVA (you can not use PVA as it is water soluble and will do nothing to seal the wall). The aim of the wall surface waterproofing is to stop the dew point moving out of the wall into the insulation anywhere. Solid walls are not very waterproof, and absolutely not if single brick hence the pebbledash or tile covering. Same goes for the blockwork & rubble below many bay windows, that has an insulation value of about 2mm polystyrene(!).

Dire thickness limitations can be solved by aerogel sheet, but it is really too expensive still - best saved for extreme situations such as tiny kitchens (limited space for 65mm PIR insulation) of very limited wall area (re aerogel cost) but diabolically cold (solid double brick with three external walls). In all other situations use PIR foam (kingspan, recticel, celotex, a couple of other brands).

[george [dicegeorge]]

Please has anyone a link to the [plastic and stainless steel 6" fixings for external Kingspan]

- do they solve cold bridging? [g]

[RobertL]

yes, "thermaboard" i think it is called. You can look up how much you need to get an acceptable U value and you can simply fix it by dabb and dotting. We have this on a bedroom with solid walls and it made a huge difference. Don't forget that if you change the U value of the wall it is a building control matter and you have to bring it right up to present standards (part L).

Robert

[RobertL]

.. or Kingspan "Kooltherm K17" here:

[Andy Dingley]

Sounds best. In general, insulating outside the main wall is better than insulating inside it, but it's often not an option. If it is, then go for it.

Retro-fit insulation is also an art of finding good compromises. You don't want to spend more in capital than is justified by the savings plus the comfort benefits. For this reason your retrofit probably will involve cold bridges that you'd work harder to avoid in a new build. Nor is a cold bridge as bad as all that - it reduces efficiency, it doesn't stop insulation working altogether.

Celotex website. Lots of really good example case studies of what to do to solve particular problems, and which products will deliver how much saving.

There are also good U value explanations around. It's really worth understanding this.

IMHE, you have to get to the level of estimating areas involved, doing the U value calculations, then the resultant heat loss calculations, then doing a damned great spreadsheet to compare the benefits with or without the expensive cold bridge solution, or thinner insulation vs. losing 2" off the room internal space. This stuff isn't trivial, but at least the arithmetic is simple enough.

[Rednadnerb]

Doesn't the foil on the celotex act as a vapour barrier? do you really have to waterproof the surface of the wall with cement slurry as well? I was hoping to get away with just dabbing thermobard to the wall in my flat which has 9" solid walls and outside render but now you've got me wondering.

[js.b1]

Yes, to you breathing in the room.

However against the outside wall (which I think you said was single brick with tiles) moisture can still condense out in the interstitial space between the foil & wall. It is how wooden battens can rot and dot-n-dab adhesive fails.

Cement slurry is only a bucket of runny quick setting cement, nothing magical, takes a few minutes.

If you telephone the various suppliers they will not suggest dot-n-dab on solid wall (eg, not suggest dot-n-dab with K17), but will on a cavity wall (eg, less chance of moisture bridging). When I telephone Lafarge re Insulated Plasterboard the first question was whether the wall was cavity or solid, when I said solid they said they would not recommend dot-n-dab but mechanical fixing only (wooden battens).