Internal wall insulation or not?

AlwaysGotAQuestion

First time user, please be kind!

Me and the OH are renovating a house we have just bought. It is 4 bed detached, quite large (ground floor is approx 90 square meters), built in around 1955 and probably not had anything done to it since other than a lick of paint!

We are putting in new double glazing throughout the whole house to replace the mainly single glazing (there is also some secondary glazing). We are also putting in a whole new central heating system with new combi boiler and appropriately sized double radiators in each room. We are insulating under the ground floor (it is a suspended floor with a 5 foot void underneath) and in between the ground and first floor. There is existing cavity wall insulation but no paperwork so we are having this checked to see if it can be/needs to be topped up. There is also loft insulation which we will top up if needed.

While we are gutting the house, the OH also wants to put internal wall insulation on the external walls in each room. You can get thermal board which is basically plaster board with 50mm insulation on the back. We would remove the existing plaster. The rooms are big enough to lose the extra 50mm all the way around. At a very rough estimate it would cost £300-£400 per room, there are 6 rooms which would be suitable for it (as we wouldn't do it in the kitchen/bathrooms) so it would probably cost between £1,800 and £2,400. The OH can do it himself so there is only labour time not cost to consider.

My concern is that with all of the other insulation measures we won't get sufficient benefit from the internal wall insulation to justify the cost and time. It is normally (as far as I can see) an alternative to cavity wall insulation so I just don't think it will make that much difference on top of everything else.

What does everyone think? Has anyone got any experience of internal wall insulation? If so, what other insulation do you have?

Any thoughts are greatly appreciated!

bridgedino

Similar to you, In two rooms in our house we internally insulated two external walls. It raised the surface temp of those walls and therefore increased the overall warmth of the rooms. I'm glad we did it.

We chose to fix timber batons to the wall, put insulating slabs between the batons and afix plaster board on top. That may be a cheaper option for you if you don't mind losing 50mm off the size of the rooms.

Take the opportunity to add/move electrical sockets as its so easy when the walls under construction

AlwaysGotAQuestion

bridgedino wrote: »

Similar to you, In two rooms in our house we internally insulated two external walls. It raised the surface temp of those walls and therefore increased the overall warmth of the rooms. I'm glad we did it.

We chose to fix timber batons to the wall, put insulating slabs between the batons and afix plaster board on top. That may be a cheaper option for you if you don't mind losing 50mm off the size of the rooms.

Take the opportunity to add/move electrical sockets as its so easy when the walls under construction

Thanks bridgedino, do you have any other insulation such as cavity wall?

The batons is a good idea.

We're already looking at sockets, you can never have too many IMO!

WestonDave

Have a look at Marmox boards - you can skim plaster directly onto these so it saves having to put insulation then plaster board then skim - it cuts out the plasterboard layer. They were intended for wet rooms etc but I've seen it used in a lounge to good effect where someone wanted internal insulation without losing as much internal space.

bridgedino

alwaysgotaquestion wrote: »

Thanks bridgedino, do you have any other insulation such as cavity wall?

The batons is a good idea.

We're already looking at sockets, you can never have too many IMO!

Yeah we got cavity wall insulation back in May and loft insulation

The house certainly holds onto its heat much much better now

System

If you have cwi already you should get someone to do a dew point calculation with the new insulation as you may be in danger of the vapour forming before it gets to a ventilated space (where your cavity used to be)

Ben84

The kitchen and bathroom are probably the two rooms I would be most interested in doing this, on account of it reducing condensation.

Otherwise, I think it's not a bad idea, but may have a very long pay back in money savings. Are you going to be using notably expensive fuel to heat the house? Also, does the existing plaster have to go anyway, because if so we should be comparing the difference over re-plastering?

Doozergirl

I love the stuff. Having lived in houses with and without, I would always take the opportunity when it is available. This house didn't really present the opportunity to us, but I regret it all the time.

That said, your house has a cavity. If the cavity is a sensible width, then that is your cheaper option. Insulated plasterboard is really the option for houses that don't have cavities.

I'd check on what you already have.

sniggings

have you looked into if the combi will be the best option?

Doozergirl

sniggings wrote: »

have you looked into if the combi will be the best option?

Combi has worked well for us in even larger houses

(As long as the pressure is there, obviously)

sniggings

Doozergirl wrote: »

Combi has worked well for us in even larger houses

no expert on this, my thought is, why wouldn't they work in a larger house but reading on here, in some cases a boiler could be the better option, cost wise and usage wise.