Skeiling insulation

[Moxi]

I'm really sorry to ask Ladies and Gents but I have read and read and read the articles here and elsweher and I'm still really uncertain of what I should and shoulddn't do.

Hopefully Biff, Wookey, Green beast or others who's posts I have read will be able to give me a simple steer.

Ok 1880's cottage West facing, North Wales, at 93m above sea level  slate tiled roof 6 skeiling sections 3 front (2 bedrooms and landing) 3 rear (1 bed 1 landing 1 bathroom) the central rear skeiling is warmest as it is inside next doors roof line (so to speak)

All I wanted to do was get some big sheets of 75mm Celotex or kingspan and cut them to fit the full skeiling then glue them to the existing painted surface taking care to ensure a seal so not air to the back then slap on some white paint to return the room to its previous state but hopefully warmer without any introduced risk of condensate. Crude but thats what I hope to be able to do. 

Would someone like to tell me (gently) if I'm bonkers or maybe just lacking confidence ?

Thanks

Moxi

[biff]

hi moxi,
     you are not the slightest bit bonkers ,.the idea is good but the teckneque is a little hairy. by that i mean that you might stick the sheets onto existing plasterboard which is not too well secured and then some night when you are having a bit of a party the lot could decend in an unwanted fashion and this you do not want. you can stick the kingspan(same thing) upright to the walls but it is taking a gamble expecting it to stay stuck to the ceiling.
          but as baldric said to black adder,"wot about the cunning plan",,,,,,,,,you could use the suspended ceiling runners to support the sheets and leave a 25mmgap between the kingspan and the ceiling,, and if you cut the 4ft x 8ft longways you get a 2ft x 8ft sheet which if supported every 2 ft would look not so bad.it would mean you would not have to run round with the filler so long as you kept the sheets from getting damaged.. and when it is all done and the double bed is in situ you wont have to fit mirrors to the ceiling nor will you come to any harm either. ponder pause and ponder again.
                                                                                                  biff

[Moxi]

Hi Biff,

What are suspended ceiling runners? I am wanting to put internal insulation on to the skeiling portion of the ceiling (this is getting confusing) as the rest of the ceiling is insulated in the loft with 400 mm of glass wool . In the skeiling portion of each room and landing there is a single beam that runs across the house and suports the rafters this makes one edge of a rectangle of plain (no battons or anything) plaster board painted white typically about 5 to 8 ft long and 4 ft wide which is the area i want to insulate.  Sorry to re-state it but as you can see I'n a real novice with older homes and whilst the rest of the cottage gets toasty there is a definate drop in temp upstairs  associated with heat loss through the skeiling so I'm keen to do something before the autumn kicks in with a vengence.  Your plan sounds perfect (even the mirrors lol ) but you lost me sadly at the first hurdle so any clarrification is most welcome.

Ta

Moxi

[biff]

on reflection moxi,
                  the suspended ceiling runners would be quite a bit of bother and finiky to boot,and i was a little confused but now i understand that you want to do that portion that slopes,??=sheiling, ? if this is the case and you only have 4ft wide to cover then by all means go for it.75mm kingspan is pretty rigid but very light over the area,however you will need to add long screws (which can reach and screw into the rafters)with a plastic washer25mmwide every 600mm x 600mm,to be on the safe side.there is a similar washer for the vertical sheets and it compresses the kingspan and finishes flush with the sheet to be filled and sanded over.
     old houses move and settle,the timbers take in moisture out of the air in the damp winters and dry out almost completely in the summer so it is understandable that expansion and contraction take place and it is this which can fight to break the adhesion between the large sheets and the ceiling or skeiling.securing the sheets with long washered screws will give you that extra safety margin so it is worth it.
     back in the threads there was another newbie who pulled of the existing plaster on the skeilings and infilles with 50mm of kingspan or similar.this was a bit of extra work but i am convinced it will be a very good job.if you have a root around you will find the thread and the advice.
                                                                                                                       biff

[Moxi]

Hi Biff thanks for the added input, I was reading about the dormer roof and watching with interest and if needed I would peel of the plaster board and go in to the rafters but TBH the skeiling internally is in mint condition and just needs that added insulation to improve the rooms and cut down thermal losses.

I have solid walls about 900mm thick and will be adding some internal insulation to those in the manner noted elsewhere in the threads later on to improve the situation but first I wanted to see if a "quick" efficient fix could be done straight away.

So my plan will be cut and shape a panel of kingspan to fit over the skeiling area snug to the beam at the top, the walls and glue and screw in to place, seal around the the edges to ensure no air transfer then fill and sand the screw heads flush and paint white to finish.

You advice is great and thank you so much for helping.

Moxi

[Moxi]

Hi AL,

Can you explain what you mean by the fire resistance please?

moxi

[A.L.]

hello,

moxi, you said on the other thread (rafter insulation with little rebuild? )

I'm going to glue and screw Kinsgspan to the existing ceiling and then fair off the screw heads with filler, sand flat and then paint, like you i need a quick win in the bedrooms upstairs before winter, if i get chance I will also start to internally insulate my 3ft walls with kingspan following the advice in some excellent threads in the forum.

to reiterate I would not be happy with a finished surface of paint on phenolic foam/polyisocyanurate in an occupied room for fire safety reasons, it will melt, give off toxic fumes etc

[biff]

hi again moxi.
            al has a good point so you can use kingspan with the plasterboard already attached to it and follow the same procedure,
                                                                                                         biff

[Moxi]

Hi Guys,

I see its more that if there is a fire the insulation is toxic in a fire so the plaster board finish gives me 30 to 45 minutes to get out before the toxic smoke starts?

Ok thats very sound advice and thank you for pointing that out I will as Biff suggests go for the pre attached stuff.

moxi

[wookey]

Your basic plan of insulating the skeilings and doing it from the inside is very sound. Anything else involves a lot of mess, and there is no disadvantage to this. I assume that you have a cold loft and that the ventilation above the skeilings is adequate? (If they are currently nothign but plasterboard then it's going to get a _lot_ colder there after insulation so if there is a condensation problem, or nascent condensation problem then it'll get a lot worse. So worth taken a look up there on a cold morning in winter (ideally both before and after the works).

But don't worry unduly - it should be fine.

OK, as biff says, glue alone on skeilings, especially if glueing to existing paint, is probably pushing your luck. At least one mechanical fixing per sheet would be sensible, which means you'll need to work out where the joists/noggins are and transfer those measurments so you can hit them after the foam is fitted.

Equally a foil surface looks a bit 'blakes 7 or 70s disco' (my house has been like this for two years now :-) so a covering is necessary, and that adds weight. You could use hardboard, but as has been mentioned platerboard has a useful fireproofing function so is generally a good idea. I'm not sure it's actually a requirement (as you already have a layer behind)- one whould have to read the regs. But's its sensible anyway.

For fixings I'd use insulation fixings to avoid thermal bridging. Fischer have a good range.

I'd do it like this:

Scrape off any loose paint to get something worth glueing to. 100mm PUR/PIR foil-faced board cut to shape/angles and PUR-glued in place. leave 8mm gap all round and gun-foam in there (you'll need an extension tube for gunning in the ceiling).

Foil-tape over any joints between sections. Insulation fixings through into joists then tape over those too.

PUR glue (or gripfix) plasterboard to foil. Really not sure what best mechanical fixing here is - as ideally you want a flush head and most of the insulation fixings aren't. One reliable way might be 20x50 battens screwed at ends and glued in the middle, i.e fixed between wall and ceiling against face of PUR. Then screw plasterboard to that. Gives you a service cavity, which might be useful. If your skeilings are much longer than about 1m then an intermediate mechanical fixing would probably be needed.

Then caulk round edges and paint.