Apply Kingspan to the EXTERIOR of house?

[Eddy]

Should we pay out for Kingspan insulation boards being applied to the exterior of our house? We bumped into a friend the other day and she was with a friend who is an architect. When he heard that we are about to have shiplap weatherboard cladding applied to the exterior of our house he said it would be easy to have Kingspan insulation boards fitted between the batons which the weatherboard will be nailed to and that this insulation would make a BIG difference to the warmth of the house inside.

The outside of our house is incredibly ugly with badly applied concrete render, or "roughcast", splattered all over it. The weatherboarding will hide all that AND also look very good once stained. But now we are wondering whether to ask the builders to fit Kingspan between the render and the weatherboard.

Previously we got a quote for tearing off all the plasterboard inside, pulling out the fibreglass wool between the studs, fitting Kingspan, applying new plasterboard in all the rooms, and skimming over. The quote was a shock! Ridiculously expensive - not because of the insulation but because of the plasterboarding and the plastering. So the whole idea had to be dropped.

But slipping Kingspan over the outside surface before nailing on the weatherboarding would be easy and wouldn't push the price up too much apparently. So the architect said and our builders agree. (They're working out a quote.)

But the big question is: would it make a noticeable or worthwhile difference to the temperature inside? What do you think? Has anybody done this already?

All feedback much appreciated.

Eddy.

[normanwisdom]

Damn good idea if your building is stone or brick and you are having weatherboarding anyway. The more the better but detailing critical i.e. if draughts can bypass the insulation then it's worthless, on a windy day especially. Also there would be an eaves detail where the new work sticks out. If not masonry then insulation outside or within the wall makes no difference in principle. Masonry would act as a 'heat sink' and slowly warm up to average room temp, radiating heat back when the heating is off, or during the night after summer daytime heat has been absorbed.

cheers Jacob

[dom]

Have a look at manufacturer recommendations:

NW says, external insulation will increase thermal mass (do you want that - or would you prefer fast warm up when you get home from work?)

Also detailing - how will substantially thicker cladding fit around window/doors/eaves/soil pipes/flues/adjoining buildings garages etc.

[The Natural Philosopher]

On balance I dont think it actually makes that much difference to heating costs - the thermal mass that is.

The rooms tend to feel warmer than they are, due to a nice ovearll retentin of warmth..you just need to advance teh tiner a bit. So let th heating come on at 4pm instead of 6, and go off at ten instead of 12pm

[mail]

Dear Eddy =46rom what you say the construction appears to be masonry with an internal stud lining or possibly structure I personally would bite the bullet and if it is 4" studwork do the internal lining. Get other quotes from 'nominated' sub-contractors and see if it really is that expensive and - as this is a DIY site consider doing it yourself! Removal of plaster board can be done by anyone (cheap labour) cutting Kspan to size is easy as is fitting it to studwork. Use foil backed plasterboard and even consider 1" internal layer over top of studs to avoid cold bridges or stud work. Much less hassle than fitting in all eaves and windows externally AND quick warm up. If you do all hte plasterboarding the only pro job will be the pinking Chris

[Eddy]

Thanks very much, Chris. I didn't want to lumber you with too much detail in the first post, so I decided not to go into the internal composition of the walls. But here goes, because I can see now that it's relevant. The ground floor of this house is thick stone, maybe 150 years old, about 18" thick. So the groundfloor keeps its heat quite well once the heating has been on for a while & warmed up the solid stone/rock walls. Also, this old stone, from the outside, looks attractive. Inside, it plastered well.

The first floor is a different kettle of fish. At some point, probably within the last 30 years, it's been rebuilt. It is entirely timber-frame. Starting from the inside we have: woodchip wallpaper, plasterboard, yellow insulation wall between timber studs, 3/4" plywood boards covering the external surface, wire attached to the plywood, then about half an inch of render/roughcast splattered onto the wire.

We've agonised about the woodchip for weeks. It's on the ceilings as well! We've been led to believe there's no getting it off without damaging the surface of the plasterboard, hence the idea of simply ripping the lot off and replacing it before skimming over - AND taking advantage of this to replace and upgrading the insulation wool between the studs with modern insulation board. We're unwilling to do all this ourselves. There's enough work to be done elsewhere round the place. And the quotes we have received to have builders do it have been horrendous. So live with woodchip we must. But with emulsion (rather than the current semi-gloss!) and a few tricks it won't look as bad as it does now.

Eddy.

[Eddy]

Thanks, Jacob.

Thanks for mentioning the effect of drafts through gaps round the insulation boards basically rendering them a waste of money. We have wondered about this. A bit like a skiing jacket: you need to pull those built-in cords around the waist, and button up round the neck, if the power of the insulating material is to be effective, the heat kept IN. We're in one hell of an exposed spot here, right in the middle of wind tunnel. So I guess this means we need to challenge the builder with the idea of sealing the insulation boards in, i.e. after they been pressed in between the batons, then a tube of sealant or something needs to be run round the edges, to make sure those drafts don't get in. What do you think?

Yes, the eaves detail would be a problem . . . if it weren't for the fact that the entire roof was in a bad state and is currently being replaced. The new one (unlike the old one) is going to overhang the sides of the house quite considerably.

So, in my very simple thinking it seems that if we can get the builder to seal the insulation boards round the edges, then the entire first floor of the house will have an additional & effective "coat" on. I've looked at the Celotex website and they state that studs act as bridges and can negate the effects of insulation, so I guess in our scenario the batons applied to the external concrete render would be the weak links, conveying cold from the weatherboarding to the render. But, in terms of coverage the batons are minor when compared to the area covered by the insulation boards.

Does this sound right to you?

Thanks a lot.

Eddy.

[Eddy]

for this, Dom. Some helpful pointers there. I also note they don't even consider how to insulate houses which are only timber-framed! Shows how "backward" our upstairs is! On the other hand, I have got to say this house is a bit like an "eco house" already. This is because the entire house is a "long house", i.e. only one-room wide. All the rooms are in a line, on both floors, and all the windows in all those rooms only face directly south AND all those windows are large windows AND double-glazed. This means that if there's any glimmer of sunshine at all, the upstairs gets somewhat heated up.

Thanks pointing out the choice between fast warm-up and slow. I guess we are stuck with slow (in the absence of sunshine), i.e. first heat will heat up the internal wals, the stud spaces & the rather flimsy woollen insulation within them, then the plywood & concrete render. But effective tight sealed draft-free insulation boards beyond the concrete render, topped with weatherboarding, ought to put a substantial stop on that outwards passage of heat. Or so it seems.

The builders know they are going to have a challenge when it comes to the upstairs window ledges, which are all UPVC. There was talk of shearing them off close into the window-frame and sealing new ones into position but I put a stop to that idea. The idea of a join filled with rubber-sealant, particularly on the south-facing side of the house, doesn't seem wise to me. Over the years gaps could occur and water get in. So they're probably going to attach some kind of surface BENEATH the current window sills to ensure rain doesn't just dribble down the weatherboarding. Anyway, thank heavens there aren't any such challenges on the first floor (doors/eaves/soil pipes/flues/adjoining buildings garages etc.) There was talk of attaching strips of down-turning lead beneath the sills. Anyway, I've said nothing is to be done until the weatherboarding is in place and we can see just how much the sills have been compromised. Maybe there are other possibilities?

Eddy.

[Eddy]

>

NP, I've little idea of thermal mass, must admit. Are you saying that if we do go ahead with slipping insulation board between the concrete render & the weatherboarding AND the insulation boards are sealed all round their edges so that there are as few gaps and drafts as possible, it won't reduce our heating bills much? This would imply that the thermostat will keep switching the boiler on as much as it is doing so at the moment, which implies that the addition of insulation boards to the exterior won't make much of a difference of the retention of heat within the rooms inside. Have I got you right?

Good point indeed, but in our case it will only be a challenge beneath our window sills.

Eddy.

[George (dicegeorge)]

i got this book from the library, it was so good that i bought a copy on amazon

i hightly recommend it to you, cheaper than half a sheet of kingspan!

Build Like a Pro: Expert Advice from Start to Finish: Insulate and Weatherize (Build Like a Pro - Expert Advice from Start to Finish) (Paperback) by Bruce Harley (Author) "There is a lot of misconception, folklore, and conflicting information about the consequences of weatherizing a house: ""A house has to breathe-you don't want it..." (more)

[Martyn Pollard]

When you warm up the solid walls, that heat is going to get drawn down through the footings straight into the earth. How quickly do they get cold when you turn the heating off? Perhaps measure it with a laser thermometer?

External dry lining with kingspan won't do anything to prevent that. I personally think the only sensible solution if you want to reduce heatloss is internal dry lining with kingspan as already suggested. DIY. Polyurethane type adhesive with one mechanical fixing per board is the quickest way. Then pay someone to skim the walls when you've drylined it.

Martyn.

[Doctor Drivel]

Eddy, use high performing KIngspan. Not to do it is foolish. Best to clad the house with Kingspan, put the outer studs over and screw through the studs, Kingspan and into the house wall. This eliminates cold bridges. Then between the studs install more Kingspan.

In the future as you do up rooms install Kingspan between the internal studs too. You get to near the point that you will not need full CH if he house is air-tight enough. Fit an insulated and sealed front door.

>

[Doctor Drivel]

It sounds like this house should have been demolished and new built in its place.

[Doctor Drivel]

It says... "Too much insulation will make your house rot,"

Which is total tripe. A house needs to get rid of water vapour, which does the damage (they call this breathing). A house doesn't need air, it needs air as the carrier to take away the water vapour. You stop the vapour getting inside walls. You stop the vapour hitting cold surfaces and condensing - this where insulation prevents a house from rotting. You extract moisture laden air at source - in bathrooms, hobs, etc. An air tight, well insulated house needs a heat recovery and vent system - a 40 watt fan slow turning extracting the moisture and bringing in fresh air.

[Doctor Drivel]

Which is total wrong. External insulation will give him all that thermal mass. Thermal mass stabilises a rooms temperature it also holds coolth and cools a house in summer.

He could dig down around the foundations and put insulation against the foundation walls underground. That will help at a lot and greatly slow the heat sink to ground.

[Doctor Drivel]

Insulate as much as possible on the outside. High performing Kingspan or Cellotex. There are others too. Keep the thermal mass. Have "wet" plaster over the stone.

Insulate the footings under the ground. This something you can do over period of time working your way around the house - keeps you fits.

[Man at B&Q]

Physician, heal thyself!

Insulation does not give thermal mass.

MBQ

[Doctor Drivel]

Physician, heal thyself!

Insulation does not give thermal mass.

[Man at B&Q]

[e-mail]...

[normanwisdom]

Well it does really - it turns the masonry into a heat reservoir (conserving heat) instead of a heat conductor (losing heat to the outside). BTW masonry is very conductive - that story of thick walls keeping houses cool in summer and warm in winter is only half true i.e. the first half, they lose a lot of heat in winter. Check out the k values you might be surprised

cheers Jacob