Insulating Kitchen Extension

E

EvenStevens

Registered User
Messages
74
I have a flat roof kitchen extension that is just quite a bit colder than the rest of the house. There is a small radiator in the kitchen and that's it heating wise. I was considering getting it wrapped externally or would I be better to replace the flat roof with a better insulated one. I can't afford to do everything so just wondering which one would make the most impact.
 
Not being facetious here, but the measure that will have the biggest impact is the one which adequately addresses the primary heat loss mechanism. To determine accurately what is happening then something like a heat loss survey is invaluable.
So, to help answer you question, a lot more info is needed (and the more accurate the info supplied the better):
  • Age of house & extension
  • Type, size etc of house and extension
  • Orientation of extension
  • Floor, wall and roof makeup of extension in detail
  • How is the kitchen heated
  • Does the kitchen heat up, hold it's heat
  • Anything else you think might be helpful
 
Hi, that's fair enough.
Have answered below.

  • Age of house & extension-House is 1948- Extension about 20 years old
  • Type, size etc of house and extension-Ex council 2 bed terraced house-standard one seen in many parts of Dublin.-Extension is flat roof and about 17m2
  • Orientation of extension-at back of house which is south facing
  • Floor, wall and roof makeup of extension in detail-Walls uninsulated concrete block, roof-timber flat roof bitumen covered, concrete floor
  • How is the kitchen heated-one radiator-gas central heating
  • Does the kitchen heat up, hold it's heat-on very cold days it doesn't hold heat. Radiator is at the door into kitchen so doesn't heat the place well.
  • Anything else you think might be helpful
 
This might be controversial but I'd probably tear it down and rebuild with proper insulation all around.
Might not be much more expensive than insulating.
Fixing only parts of it (like new roof only) will be IMO not efficient use of money.

Is the house itself insulated, e.g. internal drylining?
 

I don't actually know about internal drylining. I assume not as house is pretty old and I think the extension was the only work done to it. The house itself isn't too cold though in spite of that. Being part of a terrace helps too I think.
 
So no windows then )
how are the extension external walls finished on the inside, drylined or wet plastered (you'll know by tapping them with your knuckle)? If hollow sounding then they are likely drylined.
 
No windows . Sorry there are two double glazed windows one at the end of the extension and one on the side wall along with a back door.

Walls sound hollow alright.
 
EvenStevens said:
No windows . Sorry there are two double glazed windows one at the end of the extension and one on the side wall along with a back door.

Walls sound hollow alright.
Click to expand...
Okay, good info there.
The following will give you an idea of what may be going on with respect to your heat loss. I emphasise "may" because in the absence of an onsite inspection by experienced eyes, the following is still all theory.

1. I assume the extension is jutting out off the back wall. This means that 5 of the 6 sides of the extension (3 external walls, floor and roof) are heat loss elements and the total area of these elements in relation to the internal floor area is significantly larger to that of the original house. This means that, all things being equal, the heat loss rate will be much larger than the rest of the house. Therefore, to compensate of this increased heat loss rate, either more heat needs to be supplied to this space and/or the heat loss elements need to be optimised to reduce the losses in the first place.
2. The heat is likely being lost by a) conduction through the roof/wall (lack of insulation or insulation badly installed) and/or b) convection through roof/wall (aka draughts, air leakage). Depending on which it is will result in different approaches.
- If it's a) then you need to tackle the insulation of the walls and roof with the aim of significantly decreasing the u-value (thermal transmittance) paying special attention to the increasing risk of interstitial condensation and mould so external insulation and a warm deck flat roof detail would be advised.
- If it's b) then you need to first understand the nature of air leakage in buildings such as the extension (for example, internally drylined walls typically are devoid of an air tight barrier), how and where to rectify etc and also be cognisant of the need for appropriate ventilation to avoid indoor air quality issues and especially condensation and mould.
- or it could be a combination of a) & b)!

It is not unusual to spend a lot of money (and even receive gov grants) on a measure, for instance insulating walls & roofs, only to find out after the works are done that the problem still persists or the result is not as good as you thought it would be. This is because the cause of the heat loss was not well understood initially and the wrong measure was taken.

I'm not sure if this helps you somewhat but I want to show that questions such as yours are not always about just adding more insulation especially where a targeted approach is desired.
 
As Mickr said, it's hard to say without actually being there to see it, but, if it were me, I would consider doing the roof first. And I would have a go myself.
1. Rip off the Bitumen
2. Insulate with 100mm of PIR (on top of existing wood (minus the Bitumen as it needs to breath).
3. Cheap layer of wood on top of the PIR.
4. Layer of EDPM on top of that

This would be called a warm roof and there are plenty of Youtube videos showing how to do it properly.
 
You must log in or register to reply here.
Menu
Log in
Register