Extension doesn’t stay warm

grumbler

JoeLowe said:

Is there anything we can do to the roof space? Remove the velux windows??? / change the roof tiles to ones that insulate better? / add better insulation into the roof?

Tiles don't insulate from anything except water.

If it's some mineral wool between the rafters, then it can be replaced with a little more efficient Kingspan/Celotex insulating panels. It's a big job. Typically, there have to be at least 5cm thick panels under the rafters as well. I am not sure that this is the case in your extension because of the recessed lights.

Velux windows are there for a reason. A big extended north-facing room will be dark without them.

French door and wall windows can be triple-glazed, possibly with more energy-efficient sort of glass. Don't know if Velux do this.

Underfloor water heating can make a big difference. It works like a big heat storage. A big job again.

I assume that the floor was insulated properly and the extension was approved by the BC.

JoeLowe

Few questions:
I assume the solicitors would have checked that BC were granted for the extension when we bought the house? Where can I check? 

The roof void has no opening, so not sure how you would check what’s has been insulated with / replace what’s there. I have dropped down one of the Dow lights and it looks like it is polystyrene type substance which I assume is Celotex.

Can you change you simply just swapped glass out for triple glazed or would it be a new frame as well? 

Doozergirl

JoeLowe said:

Few questions:
I assume the solicitors would have checked that BC were granted for the extension when we bought the house? Where can I check? 

The roof void has no opening, so not sure how you would check what’s has been insulated with / replace what’s there. I have dropped down one of the Dow lights and it looks like it is polystyrene type substance which I assume is Celotex.

Can you change you simply just swapped glass out for triple glazed or would it be a new frame as well? 

The difference in energy saving between current double glazing and triple isn't seen back in the bill savings. 

Are you going to ignore the idea of a thermal imaging camera so that you don't need to guess?   

Yes, you have a lot of glass, but it's not a huge amount more than most people are putting into these houses these days.  

tacpot12

If you can see what looks like polystyrene in the roof void, it might well be XPS or EPS (Extruded or Expanded Polystyrene respectively). Both are good insulators, but there is not much thickness to the roof so their might only be 50mm between the rafters rather 300m over the rafters.  An earlier poster said it would be a big job to increase the thickness of the insulation in the roof. I would disagree. You can remove the existing tiles and insulation, and install a "warm roof" on top of the existing rafters, and reinstall the same tiles over the top. This is well within the capability of a competent DIY'er. Actually I would tend to advise doing it yourself, as most roofers don't understand how to build a "warm roof" - the term has a very specific meaning in building technology. As with all roofing, it is the attention to detail that will ensure it is successful.

The Roof Lights will probably have a manufacturer's label on the side of the frame somewhere. If you can find this, you can contact the manufacture to see if they can supply higher performance glass units to fit into the frames you have. If they can't it will mean new frames, and the risk that the old tiles cannot be made to fit around the new frames as well as they do around the old frames if you do decide to install a warm roof. 

Did you tell the solicitor about the extension? If not, they may not have asked about Building Control approval for it. You can check directly with your solicitor, but expect them to be a little defensive. You might suggest that you want them to check their records as you're not clear the extension was built to the building regs and you might want to sue the vendor - solicitors like it if they think you might need to pay for more legal advice... 

Jeepers_Creepers

A few things I think should be considered:

How much better is 100mm rather than 50mm 'Celotex' at insulating? Answer is - I don't know (can't be bovvered to look it up) but I'd hazard it's no more than 10% better. Why? Because the 50mm thickness has done most of the work, already reducing heat transfer by - what? - 80%? So the additional thickness is only going to reduce the remaining 20% by a further 80% = not a lot.

For how much of the year do you need to heat this room anyway? And how much extra does this cost - £100 pa absolute max? Compare that with the £ks it'll cost to alter anything in there.

Is it worth it? No, it isn't. That's a nice room - enjoy it and keep it warm whilst you use it.

If a gale blows the roof off, then you can add stuff. :-)  

grumbler

You are mistaken. 100mm is twice as good as 50mm. Thermal resistance is directly proportional to the thickness. And the heat flow is inversely proportional to the resistance. It's very similar to electricity.

ETA: That said, if, say, 90% of the heat loss is through the walls, glass doors and windows, it will hardly make any change if you reduce the loss thought the roof from 10% to 5%.

JoeLowe

Are you going to ignore the idea of a thermal imaging camera so that you don't need to guess?   

Yes, you have a lot of glass, but it's not a huge amount more than most people are putting into these houses these days.  

Thermal camera - I’ve been looking at they appear to be around £300 for a decent one. 

Any recommendations as will only need it for the once?

Doozergirl

JoeLowe said:

Are you going to ignore the idea of a thermal imaging camera so that you don't need to guess?   

Yes, you have a lot of glass, but it's not a huge amount more than most people are putting into these houses these days.  

Thermal camera - I’ve been looking at they appear to be around £300 for a decent one. 

Any recommendations as will only need it for the once?

They are pretty widely available to hire! 

JoeLowe

tacpot12 said:

If you can see what looks like polystyrene in the roof void, it might well be XPS or EPS (Extruded or Expanded Polystyrene respectively). Both are good insulators, but there is not much thickness to the roof so their might only be 50mm between the rafters rather 300m over the rafters.  An earlier poster said it would be a big job to increase the thickness of the insulation in the roof. I would disagree. You can remove the existing tiles and insulation, and install a "warm roof" on top of the existing rafters, and reinstall the same tiles over the top. This is well within the capability of a competent DIY'er. Actually I would tend to advise doing it yourself, as most roofers don't understand how to build a "warm roof" - the term has a very specific meaning in building technology. As with all roofing, it is the attention to detail that will ensure it is successful.

The Roof Lights will probably have a manufacturer's label on the side of the frame somewhere. If you can find this, you can contact the manufacture to see if they can supply higher performance glass units to fit into the frames you have. If they can't it will mean new frames, and the risk that the old tiles cannot be made to fit around the new frames as well as they do around the old frames if you do decide to install a warm roof. 

Did you tell the solicitor about the extension? If not, they may not have asked about Building Control approval for it. You can check directly with your solicitor, but expect them to be a little defensive. You might suggest that you want them to check their records as you're not clear the extension was built to the building regs and you might want to sue the vendor - solicitors like it if they think you might need to pay for more legal advice...

Roof lights? Do you mean the velux Windows? They have a code on them which I’m going to look at into more detail. 

Warm roof - I will have a look at that. I’m going to see if I can remove a down light and see what is in the roof void.

JoeLowe

Just looking through my paperwork for the house and can see the roof was insulated with 100mm celotex.

It also mentions 12.5mm to plasterboard as an internal finish.