Cold loft conversion (Ed.)

[tommys1985]

Hello,

I did a loft conversion last year in December 2022 and according to the builder 125mm cellotex insulation has been used. Rockwool has been used on the floor. The temperature is not maintained even when heating is on and rapidly losses temperature, it just feels cold. Is this normal? Searching around I am being told that the loft should be the warmest room in the house as the heat rises. Any suggestions if this is normal or something has been missed and how to fix it?

 

[Roy Bloom]

Insulating the floor has stopped the heat rising.

 

[freddiemercurystwin]

Insulating the floor will retain more heat in the floor below, did you need it for fireproofing? Do you have any photos of the work? Are the dwarf walls insulated, a lot of it comes down to how well it was done. Are the radiators adequately sized?

 

[cdbe]

There isn't much thermal mass to store the heat. Larger rads/separate zone with longer on time is probably the best you can do.

 

[Dereekoo]

According to the builder?is it 125 or not

 

[Terrywookfit]

I recently completed my loft conversion. The rad never comes on and it is still the warmest place in the house,

 

[Mottie]

Loft conversions. Hot in summer, cold in winter.

 

[^woody^]

Lofts prior to the recent regs change should normally be 150mm total roof insulation, and if so would be excellent at being warm with minimal heat input. 125mm would be less efficient, but should not be cold.

Have the heating emitters been suitably sized?

if so, perhaps there are design issues with cold bridges or quality issues with gaps and draughts in the insulation layer.

 

[JohnD]

Use a smoking joss stick to search for draughts.

Feel all surfaces with your hand to see which are cold.

If true, 125mm foam slab is plenty.

If true.

 

[tommys1985]

I recently completed my loft conversion. The rad never comes on and it is still the warmest place in the house,

can i please ask what temperature you are maintaining in the loft these days ?

 

[tommys1985]

Insulating the floor will retain more heat in the floor below, did you need it for fireproofing? Do you have any photos of the work? Are the dwarf walls insulated, a lot of it comes down to how well it was done. Are the radiators adequately sized?

I did it to reduce the sound from loft to first floor. Radiators are sized as per the calculations on room size, btu etc. The loft warms up but loses heat very quickly. 4-5c in 6 hours or so.

 

[JohnD]

Radiators are sized as per the calculations on room size, btu etc. The loft warms up but loses heat very quickly. 4-5c in 6 hours or so.

The heat is getting out somewhere. Draughts or gappy insulation.

The calculations lead to undersized rads, but deal with that later.

 

[tommys1985]

The heat is getting out somewhere. Draughts or gappy insulation.

The calculations lead to undersized rads, but deal with that later.

if it's gappy insulation, what options do i have? i dont want to take down all plasterboards, can i add insulation from the top of the roof by removing the tiles?

 

[JohnD]

if it's gappy insulation, what options do i have? i dont want to take down all plasterboards, can i add insulation from the top of the roof by removing the tiles?

You could do, but it would be a lot more work and expense. Once you have identified where the problem lies it will be easier. Try crawling round the eaves space with a torch and your joss stick.

Is your roof felted? Or does it have a permeable membrane?

 

[tommys1985]

You could do, but it would be a lot more work and expense. Once you have identified where the problem lies it will be easier. Try crawling round the eaves space with a torch and your joss stick.

Is your roof felted? Or does it have a permeable membrane?

i cant travel in eaves as it is boarded up. roof is a membrane from what I remember and it is tiled.