Rough estimate and requirements for loft eaves?

Liquid_Entity · 5 Jun 2022 at 13:45

Hi all,

Moved in Nov 2020 and the loft extension was already converted a long time ago. We've gone through a summer and 2 winters now and this room gets super hot and super cold. It's our 6yr olds bedroom and I want to make it more warmer in winter and cooler in summer.

It needs a good clear out but also what do we need to do to make it more efficient at heating and cooling and for easier storage and of corise the supplies and costs.

Semple · 5 Jun 2022 at 14:38

Storage part is easy, just a case of boarding over the joists.

Heating and cooling will be very tricky though, lots of people seem to have problems when it comes to using the loft room as a bedroom. I presume it's connected upto the central heating? Have you measured the temperature in the winter? Similar for the summer, does it have windows that can be used for a bit of ventilation?

Liquid_Entity · 5 Jun 2022 at 14:41

Hey, yeah it's got 2 velux windows and a radiator all connected up.

radderfire · 5 Jun 2022 at 15:03

I wouldn't call myself an expert, but the thermal performance is likely to be related to the quality of insulation in the eaves and in the floor.

Also, I don't get the pictures - you say the loft conversion was done a long time ago, but you show us unfinished pics first, and then a finished room?? Are you talking about a space next to the bedroom?? Are you asking about improving the finished room shown, or doing something about the unfinished space??

Liquid_Entity · 5 Jun 2022 at 15:19

These are the spaces leftover after the conversion.

robj20 · 5 Jun 2022 at 15:29

Doesn't look like they insulated that correctly at all.
Get rid of the current insulation and replace it with PIR type. It's roughly twice as efficient.
I just replaced 75mm of the fluffy stuff with 140mm PIR when I boarded my loft.
If you go fluffy stuff you need around 280mm.

Lean · 6 Jun 2022 at 07:30

As above. The insulation is inadequate. The 100mm rafters can't hold enough rockwool. You may have a bigger job on your hands than you want.

You may need to strip the plasterboard, remove the wool and put some PIR between the rafters (batten them out to get your depth). Reboard and skim/dry line. You'll lose a bit of headroom but it will be a much nicer space temperature wise to live in. Insulate those studwalls as well.

robj20 · 6 Jun 2022 at 07:36

How old is the conversion, isn't it a requirement to abide by the regulations regarding insulation?

Scam · 6 Jun 2022 at 10:26

Funny this thread came up as I've just had a discussion with our builders about what insulation goes in our eaves storage area. (Our loft is a work in progress, boarded out and insulated, battened, but no tiles on roof yet). We assumed it would be the same as the room itself (100mm Celotex/Kingspan on floor, 120mm on roof) but they've just taken away the remaining stuff and the guy seemed to think we only get 25mm inbetween the rafters. I think they've done the 100mm floor. Is this going to be adequate? Girlfriend is horrified it's not the full 120mm as per the rest of the roof, especially as where the bed is going to be she will be sleeping next to that area! :confused:

Derek W · 6 Jun 2022 at 13:24

Liquid_Entity said:
Hey, yeah it's got 2 velux windows and a radiator all connected up.

The haphazard insulation that's there will be an issue but is the hatch behind the hoover insulated on the back as that will draw out any heat if it isn't?

robj20 said:
How old is the conversion, isn't it a requirement to abide by the regulations regarding insulation?

This may be a concern if it hasn't been done to the standards of the time.

Scam said:
Funny this thread came up as I've just had a discussion with our builders about what insulation goes in our eaves storage area. (Our loft is a work in progress, boarded out and insulated, battened, but no tiles on roof yet). We assumed it would be the same as the room itself (100mm Celotex/Kingspan on floor, 120mm on roof) but they've just taken away the remaining stuff and the guy seemed to think we only get 25mm inbetween the rafters. I think they've done the 100mm floor. Is this going to be adequate? Girlfriend is horrified it's not the full 120mm as per the rest of the roof, especially as where the bed is going to be she will be sleeping next to that area!

What do you mean they've taken away the remaining stuff? The stuff that's already installed or any offcuts? The sloping ceiling definitely needs to be more than 25 mm though :cry:

that level of insulation may have been fine in the 1980s though! What did your architect specify on the drawings and what uvalue are you trying to achieve?

Liquid_Entity · 6 Jun 2022 at 16:02

I'm not on my work laptop today and all the original paperwork from the sale and solicitor stuff is on there. I recall it being around 30 years though so early 90s.

Scam · 6 Jun 2022 at 16:16

Derek W said:
What do you mean they've taken away the remaining stuff? The stuff that's already installed or any offcuts? The sloping ceiling definitely needs to be more than 25 mm though that level of insulation may have been fine in the 1980s though! What did your architect specify on the drawings and what uvalue are you trying to achieve?

No just the unused leftover stuff. Builder's quote says this;

100mm Celotex / Kingspan insulation to external walls
Clad Rear dormer with Plain Tiles to match existing front slope color.
126mm Celotex/Kingspan insulation to flat roof
120mm Celotex/Kingspan insulation to front slope

Architect's drawings says this - doesn't really call out the eaves storage area which is why we assumed it was the same;

So the floor is already insulated with rockwool, and they've put the Celotex stuff on the interior wall although we've got two big doorways for access which will lose a lot of heat unless they are insulated as well! Reason we asked is because on the front slope (in the storage area) there's no insulation yet.

EDIT: Builder has said;

Only the small wall is insulated as building inspectors want a flow of air in that area to keep timbers dry. Many clients wait until loft is signed off and then they sometimes fit 25mm solid insulation to underside of rafters

alexakasloth · 6 Jun 2022 at 16:22

It would be worth starting with the eaves to make sure they are correctly insulated on the dwarf wall facing the room. I think it should be, if using PIR (celotex etc) around 120mm foamed & taped.

Buffman · 7 Jun 2022 at 08:13

The architects drawings identifies celotex (i.e. Solid board insulation with a better U value) but from the look of your photo you can see glass fibre insulation coming out of the rafters (ie the sloped roof) ? Is that the case?

Scam · 7 Jun 2022 at 10:00

Buffman said:
The architects drawings identifies celotex (i.e. Solid board insulation with a better U value) but from the look of your photo you can see glass fibre insulation coming out of the rafters (ie the sloped roof) ? Is that the case?

Don’t confuse me with the OP. I was jumping into a relevant thread as the subject had literally just come up for our eaves.

Buffman · 7 Jun 2022 at 12:06

Scam said:
Don’t confuse me with the OP. I was jumping into a relevant thread as the subject had literally just come up for our eaves.

Woops would help if I read properly!

But yes, typically you would use solid insulation like celotex as per unit depth it has better insulating properties.

It looks like the OPs conversion has not used good insulation materials. I'm not a loft conversion expert but imagine youd need to break out all the plasterboard in roof, potentially batten out and put in celotex/similar (whilst maintaining an air gapl. For the floor youd have to do similar.

Obviously that's a significant undertaking!

If I was early 90s built, building regs wouldn't have had the more modern requirements for insulation.