Internal insulation - solid walls.

[MontyMonty]

Hi,

We have an end of terrace 1920s built house. Walls are solid.

The hall gets very cold in the winter. Things got worse when we stripped the wallpaper and reskimmed the plaster a couple of years ago. We are looking at trying to insulate the wall. Problems is we don't have a large budget and can't afford to lose any space into the stairwell. Stairs are quite narrow as it is.

Best option I can come up with so far is Marmox 10mm insulation board stuck to existing plaster and then reskimmed. We should just about get away with this without changing sills etc.

Anybody used this stuff before? Is it likely to make a difference. Also looked at Wallrock thermal liner (4mm) but assume the insulation board would be better.

Grateful for any advice.

 

[noseall]

The most recent solid wall we insulated involved using 40mm insulation plus plasterboard total 52.5mm. This was fixed to 25mm battens.

You could improve things with thin insulation but not a great deal. You may not even notice the difference using 10mm.

Unfortunately there is no magic thin insulation or we would be using it.

 

[MontyMonty]

Thanks, noseall.

Very frustrating. Wish we had more options.

For what it's worth I now think we can use the 12.5mm insulation boards. Spec says it has a thermal reistance "R" value of 0.36. Means nowt to me.

Can anybody suggest any better options? Absolute max depth is 15mm.

 

[^woody^]

It won't matter much in a hallway whatever you do, put a bigger heater in

 

[MontyMonty]

Thanks.

Already got a big double convector rad in the hall. No space for anything else.

Unless I can find anything else I may as well go for it. Even if the improvement is minimal it is better than nothing.

 

[MontyMonty]

One more thing.

The specs for the 12.5 mm insulation board have this stat:

Thermal Transmittance
(W/m² x K) 10OC ambient
temperature difference

2.69

Confusingly (for me) the number decreases as the boards get thicker.

Excuse my ignorance but can anybody advise what this means?

Cheers.

 

[jabuzzard]

You probably have a suspended timber floor. You could try insulating that, it will help. Also check for air tightness especially around the skirting boards. If it is bad which it almost certainly is pull them off, seal with silicone and replace (probably easier to bin and ditch the lead paint and fit new).

Also what insulation is there under the stairs? In my 1950's house underneath the bottom 10 stairs it is just open to the sub floor void. I cut 100mm Celotex board up and insulated the underside of the stairs held in place with nails. For me I had easy access from underneath the floor boards, so this might be harder for you.

Sometimes you also have large area above the stairs. You might be able to frame this off reducing the space you have to heat, thus keeping the rest of the hallway warmer.

I would look into these before trying to insulate the walls.

 

[noseall]

Cold houses or rather cold spots in houses can be attributed to draughts far more often than lack of insulation.

When we construct a building we are more vigilant than ever when it comes to alleviating draughts and take care to reduce the risk of draughts.

 

[MontyMonty]

Thanks for all your comments. Very helpful.

Will give some thought to insulating floorboards and under the stairs. And tackle those draughts. Probably need to bite the bullet and up my budget. We have an old wooden door so should think about replacing that.

 

[jabuzzard]

Thanks for all your comments. Very helpful.

Will give some thought to insulating floorboards and under the stairs. And tackle those draughts. Probably need to bite the bullet and up my budget. We have an old wooden door so should think about replacing that.

You don't say what your hall floor covering is. If it is just the original bare floorboards then that is your problem right there. My mother is constantly amazed at these retro trends that were abandoned for something more practical as increasing wealth and technology allowed.

If you have some other covering over the floor, then the boards are perfectly reusable if care is taken taking them up to install the insulation.

As noseall says draughts make a massive difference. Insulation won't help if all your warm air is leaking out the building.

I have just done my lounge in a 1950's suspended timber floor house this year and when I took the skirting board off (it's was covered in lead paint and it is quicker, cheaper, simpler to just replace with new) there was a substantial gap all the way around. I used a bag of browning plaster (its cheap) to fill the gap up between the floor boards and the wood strip the skirting was attached to. Even then in places I had to cut strips of wood in places as the gap was so wide. You can feel the room is a lot less draughty now.

If you have carpet, then I would recommend putting paper down before the underlay, it makes more difference than you might imagine.

Check the draught excluder round the front door, letter box etc. One thing that can make a major difference is a curtain over the front door. Also make sure any central heating pipes under the floor are insulated, otherwise you are wasting heat that could be going into the hallway.

Does the hallway have any windows, and if so are these double glazed? A squirt of silicone around where the electric cables penetrate the ceiling for the lights won't go amiss.

Something else that might seem a little perverse is to stick some loft insulation under the floors of the upstairs rooms. This helps keep heat downstairs; also stopped my bedroom from getting too hot.

I would say there is plenty that you can do to improve the situation before you look at insulating the walls and at less cost.

If after all the alternative measures it is still too cold, then I would hack all the plaster off the external walls to get back as much depth as possible and install the thickest aerogel panels (twice as effective as kingspan/celotex) you can get you get away with and reskim. This will not be cheap however and I would say should be considered as a last option.

 

[iwaters]

There is a new govt. initiative which allows you to purchase energy efficiency products and pay through the savings on your energy bill.

As part of this there is govt. funding available for hard to treat properties such as solid walls and narrow cavities, called ECO, Energy Company Obligation.

You should be able to get proper solid wall insulation and not pay for much. Doesn't kick off properly until the new year but might worth considering?

 

[DIYedboy]

The cheapest way to make your hall warm is to buy a really thick n heavy curtain off ebay and fit over the door (make sure it touches the floor).............you'll be surprised by the difference

 

[DB1]

... when I took the skirting board off (it's was covered in lead paint and it is quicker, cheaper, simpler to just replace with new) there was a substantial gap all the way around. I used a bag of browning plaster (its cheap) to fill the gap up between the floor boards and the wood strip the skirting was attached to. Even then in places I had to cut strips of wood in places as the gap was so wide. You can feel the room is a lot less draughty now.

Hi, I don't mean to worry you but I would have thought that gap had a reason for being there, I think it's to stop 'thermal bridging' between the plaster on your wall and the cold floor. So yes you are right it will now be less draughty - but won't you now get the cold creeping up the wall which will result in condensation on your walls and then dampness and eventually maybe even mould?
I just had a damp and timber report done for a house I am about to buy and it provided a plastering specification which included that gap you mentioned - it says leave a gap of at least 40 mm.

I think the underfloor insulation is a good idea but again you need to make sure air can circulate and take any moisture away i.e. make sure the insulation doesn't cover up air bricks.

 

[jabuzzard]

Hi, I don't mean to worry you but I would have thought that gap had a reason for being there, I think it's to stop 'thermal bridging' between the plaster on your wall and the cold floor.

You don't think the brick wall does that cold bridging for you? For the avoidance of any doubt that is a rhetorical question because it does. It's pretty basic thermodynamics really.

My understanding is that the gap exists because there is usually a wooden strip called the "ground" that is used as a level for the plastering and to attach the skirting board to. You don't plaster all the way to the floor as otherwise you would pick up dirt that would make a mess of the plastering.

So yes you are right it will now be less draughty - but won't you now get the cold creeping up the wall which will result in condensation on your walls and then dampness and eventually maybe even mould?
I just had a damp and timber report done for a house I am about to buy and it provided a plastering specification which included that gap you mentioned - it says leave a gap of at least 40 mm.

There are arguments about damp, but if you have a functioning damp proof course it does not apply. Note that the requirement for damp proof courses was introduced in 1875 by the Victorians, so a 1920's house should have one.

I think the underfloor insulation is a good idea but again you need to make sure air can circulate and take any moisture away i.e. make sure the insulation doesn't cover up air bricks.

It should also not be any deeper than the timber joists. That is the bottom of the insulation can come to level with the bottom of the joists but no further. In Scotland building regulations now require suspended timber floors to be insulated.