How do you know what insulation is good enough?

Soldato
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With regards to loft conversions. What do builders normally quote as standard? We were speaking to our neighbours and looking at their conversion, they mentioned it can be a bit cold up there which I was surprised about. Especially considering they put 3 radiators up there (although I think they were talking about without the heating on)

Our builder has quoted the below. Obviously we'll chat with him about options but is there anything separately/online I can be looking at to compare?

(snip)
  • Create new timber floor with C16 Joists and laying 100mm insulation in between timbers.
  • Board out new floor in 22mm moisture resistant chipboard
  • Build Box shaped dormer.
  • 100mm Celotex / Kingspan insulation to external walls
  • Clad Rear dormer with Plain Tiles to match existing front slope color.
  • 126mm Celotex/Kingspan insulation to flat roof
  • 120mm Celotex/Kingspan insulation to front slope
  • GRP fiber glass to flat roof.

Likewise, sidenote... We've opted for clay tiles rather than bog standard onces. And not slate which a few have gone for on our road. Besides cost and aesthetics is there anywhere I can find out what the difference in 'performance' is? :)
 
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You may want to consider wind noise as well. My brother had his Loft conversion 2 years ago and they struggle with wind noise when it is windy, especially as their Juliette Balcony faces SW which is the main wind direction. They are also on the Heathrow flight path and they suffer with aircraft noise, especially with older chapter aircraft on final approach. The dormer element of his loft conversion is clay tile clad and they contribute to the additional wind noise, especially when the wind gets under the tiles. Just food for thought.
 
Soldato
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@SimonR good points thank you. Hadn't thought of that. We are on the flightpath too, when the weather is good they seem to take-off almost along our street now which is obviously a lot noiser than when landing :p The dormer (rear) will be south facing. Mind you all this applied in our old flat where the bedrooms were in the converted loft so as long as it's not 'worse' than that was I'm sure we can manage. I dont know how well the loft was converted/insulated in the flat.

What about triple glazed velux windows? Worth the extra? Or will you get plenty of rain noise through the roof regardless?
 
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Cant add anything specific other than observation.
Having lived in a higher level house (multi story) like your going to, if you ones to have doors open then the higher floors will be warmer than lower. As such the insulation at the top will be more critical than ever with energy costs going the way they are

Also again an observation, round me are roughly 50/50 between 2 (with traditional loft) and 3 no loft over the top, and when its been really cold its very obvious the ones with a traditional loft (all round us will be 270mm of insulation due to age) are far better insulated than those with no loft.

So based on both of above, I would go over spec as much as poss on a dormer conversion. Deffo triple glazing (it adds more comfort via less drafts than outright insulation but still..) and see if you could go to 200mm or so of PIR easily. It would add negligible cost, but it can only help.
I would also keep an eye and make sure they are really doing a good job on the insulation, not cutting corners, properly taping etc. It will make a big difference.
 
Soldato
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I don't think triple glazed velux windows will muffle rain sounds (frankly i'd prefer that as i find rain quite therapeutic to fall asleep to, but that's another discussion :D), but they should be better at retaining heat, and external sound.
 
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Heat is your only other consideration. Ours is a modern 3 storey, 6 bed with 2 bedrooms on the top floor. As well insulated as the house is, heat rises and in summer the top two bedrooms get warm. It isnt helped by a central spiral staircase which acts as a chimney. I think in hindsight I'd have considered aircon for the top two bedrooms just to make them more comfortable in summer. Fortunately we dont sleep up there as one room is our cinema room and the other is the wife's yoga studio.
 
Soldato
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With regards to loft conversions. What do builders normally quote as standard? We were speaking to our neighbours and looking at their conversion, they mentioned it can be a bit cold up there which I was surprised about. Especially considering they put 3 radiators up there (although I think they were talking about without the heating on)

Our builder has quoted the below. Obviously we'll chat with him about options but is there anything separately/online I can be looking at to compare?



Likewise, sidenote... We've opted for clay tiles rather than bog standard onces. And not slate which a few have gone for on our road. Besides cost and aesthetics is there anywhere I can find out what the difference in 'performance' is? :)

My parents did a proper loft conversion when i was still up home with 100mm celotex and in the winter I barely had the heating on up there. No dormers, but 100mm should give you a pretty good shield from most of the elements providing as others have said you've got a good warm house underneath, in winter this will help but in summer could cause it to be quite hot.
 
Soldato
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The issue with a loft conversation is that the thicker you make the insulation, the less space and head room you have. But as others have said, more is better and you should go as think as you can with the highest performing insulation you can afford.
 
Soldato
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Deffo triple glazing (it adds more comfort via less drafts than outright insulation but still..) and see if you could go to 200mm or so of PIR easily. It would add negligible cost, but it can only help.
I would also keep an eye and make sure they are really doing a good job on the insulation, not cutting corners, properly taping etc. It will make a big difference.
So you're saying where he has quoted 100mm-126mm we should be asking for more? Before he quoted we already made noises about wanting a warm house (my girlfriend is permanently cold). But perhaps we'll have another conversation about it.

Heat is your only other consideration.
The aforementioned neighbours next door went for a big picture window on the rear dormer. Not only does it not match the Edwardian terraced style, but they were complaining that it's super hot when the sun hits as the back of our houses are south facing :p (Maybe the cheap picture window is a reason their loft gets cold? :confused: ). We'll have two sash windows instead, with shutters to shut when the sun hits. Should help.

The issue with a loft conversation is that the thicker you make the insulation, the less space and head room you have.
We're ok for head room. 2.3m at the peak/dormer. Quite a sharp incline on the front slope mind.
 
Soldato
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Big window won't help, they let out about 4-5 times more heat than 100mm of polystyrene insulation I think.

as above get more insulation in there if you have the headroom, extra 25mm to 150mm will make a chunk of difference, regards the Velux and noise, you barely notice it once you're used to it, unless it's actually hammering it down which happens a handful of times per year.
 
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that's plenty...... UK building regs is 100mm PIR, Scottish is 125mm PIR (from memory)

I've got 120mm and 75mm on the walls and with the heating off it never really gets cold

Good to see they've specced insulation the floor, otherwise all the rooms underneath would get significantly colder

I went with the double glazed laminated Velux windows which are rated better for sound than the triple glazed I think
 
Soldato
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Big window won't help, they let out about 4-5 times more heat than 100mm of polystyrene insulation I think.
That was my point. I think they made a mistake with the big window. We have tiny gardens too so you're not exactly looking out over lush farmland or anything, just straight into the neighbours house approx 12 metres away :p (No idea why some people have opted for juliet balconies with these small houses!)

Good to see they've specced insulation the floor, otherwise all the rooms underneath would get significantly colder

I went with the double glazed laminated Velux windows which are rated better for sound than the triple glazed I think
Yeah the whole house needs an overhaul, the kitchen/side return needs insulating properly as well, it's just bare brick and the cupboards against the exterior wall are approx 10c in the cold weather - with the heating on! Good for storing beer mind but you're shivering late at night before going up to bed. Can't wait for that to be done, and the new kitchen obviously.

Good note re. the velux windows. I will ask about that. The builder seems very detail-orientated which is why we liked him. He's also done lots around here including much bigger houses, so we're confident everything will be done to a certain level.

Edit: Any thoughts on roof tiles?
 
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Soldato
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Sorry to sound daft but it mentions a flat roof, surely that limits insulation thickness more than an apex?
It's a rear dormer being added to a terraced house. I meant the peak of the roof is 2.3m currently, so the dormer will be that height too.

(I'm sure it'll all be a bit less in the end, but there's plenty of head height either way)
 
Soldato
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Robin is class, I watch all his videos - he use to be on skillbuilder quite a lot as well.

Anyway, you could always get an A/C unit put it and hide all the services behind, that’ll give you both heating and cooling when required. Get it done by someone in the business though and put in a decent unit like Mitsubishi m or slim (not their Heavy Industries range) or Daikin.
 
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