Experience before and after room in roof insulation

[MattyP182]

Hi all,

Any one done this or had it done and do you have any numbers on how the heat requirement of these rooms changed subsequently?

I'm just thinking through what the options are and if worth it for the hassle/risks i.e.
-Will it make much difference (filled cavity walls, double glazed but 20+ years old (will replace), 60's house, 270mm loft insulation fitted). Heating stats of larger room in roof is currently 62W/m2 (13m2 area 0.805kWh to maintain 15C indoor with 1C outside temperature)
-Worried about the usual, mess of having it done, (stud wall needs exposing/modifying to provide sufficient ventilation gap to roof on sloped sections), added ventilation through roof maybe required, condensation/mould/rot if not done right-industry seems like a mine field
-Might want to fit flush cupboards into dwarf walls to make use of eaves space but not sure how/if this would compromise the effectiveness of any added insulation
-Would retrofitting a warm roof be a more all encompassing solution? Roof tiles are 60 years old, will need replaced at some point. Would favour paying more if it means less internal rework to fit insulation and deal with it from the outside envelope, cavity walls/roof if possible?

Thanks for your feedback

 

[StephenStephen]

What is 'room in roof insulation'?

 

[noseall]

What is 'room in roof insulation'?

Loft conversion insulation.

 

[noseall]

Hi all,

Any one done this or had it done and do you have any numbers on how the heat requirement of these rooms changed subsequently?

I'm just thinking through what the options are and if worth it for the hassle/risks i.e.
-Will it make much difference (filled cavity walls, double glazed but 20+ years old (will replace), 60's house, 270mm loft insulation fitted). Heating stats of larger room in roof is currently 62W/m2 (13m2 area 0.805kWh to maintain 15C indoor with 1C outside temperature)
-Worried about the usual, mess of having it done, (stud wall needs exposing/modifying to provide sufficient ventilation gap to roof on sloped sections), added ventilation through roof maybe required, condensation/mould/rot if not done right-industry seems like a mine field
-Might want to fit flush cupboards into dwarf walls to make use of eaves space but not sure how/if this would compromise the effectiveness of any added insulation
-Would retrofitting a warm roof be a more all encompassing solution? Roof tiles are 60 years old, will need replaced at some point. Would favour paying more if it means less internal rework to fit insulation and deal with it from the outside envelope, cavity walls/roof if possible?

Thanks for your feedback

Does the existing roof have breathable membrane or through ventilation?

 

[MattyP182]

Basically bedrooms & bathroom upstairs are in the roof. It's a two floor chalet style house. The dwarf walls (silver backed plasterboard currently) are around 1.6m tall then it slopes to the ceiling. The eaves area on one side has a hatch and has been used to run a water pipe & storage basically but can then see the sarking board fixed to roof rafters. Basically there is only plasterboard protecting us from the eaves area which can get down to 3C when cold out. There is a loft also and this floor has been insulated. There are no vents in the eaves area through the roof, but it seems to be a fairly draughty space anyway.

 

[MattyP182]

 

[Ivor Windybottom]

My experience of a previous converted bungalow we owned was that it makes some difference, but by far the biggest issue we had was that the air was blowing straight through the floor/ceiling between the two floors as the joist ends were left open. It was near impossible to access to stuff insulation in due to the tunnel around the perimeter being too small to even crawl inside.

Doing it as part of a re-roof is probably the only sensible solution. In which case you may need a scaffold roof over as you'll have the place open for a few days.

I'm now very glad to own a larger bungalow with no loft conversion and no plans to add one!

 

[MattyP182]

Ok thanks. In our case, the space is big enough to get in, you can't stand but you're not crawling on your knees either. The dwarf walls could be done from the eaves side but on the sloped sections where the plasterboard runs parallel to the roof, the gap on the eaves side is rafter depth (100mm + about 80mm). So this is where it either needs to be done from in the room and lose a bit of ceiling or remove plasterboard from room side and fit 100mm insulation between the joists rafters which would leave the 80mm gap to the roof sarking board.

From someone who has no experience of any of this It would be easy to say oh just do a warm roof but I'm sure it has it's own complications and I've not researched it too much. Another thing when not done right could be more disastrous..

 

[cdbe]

Potentially a lot of disruption to do the rafters from inside - I believe people have managed to achieve something reasonable by carefully feeding PIR boards between the rafters - up from the eaves and down from the top loft - while maintaining a 50mm air gap between insulation and roofing felt.

 

[MattyP182]

Yes I did have that thought to slide down from loft/up from eaves but don't think it would be good enough. I.e. would be gaps, cold bridges? and no way to seal to stop vapour. Certainly easier to do nothing! It's disruption/pay out Vs real gain. If someone could say you'll half your heating bills I'd probably do it but I suspect it's more subtle, more like 10% reduction in bill/gas use