cost of cellulose

tfer

I am hoping to start a TF house this summer and am trying to put costs together, the boards have been great reading, but i cannot find prices by anyone cellulose insulation in 140mm studs @ 400c. Does anybody have per sq m price, thanks.

soldsold

14 euro per m2 cash price from my supplier

tfer

thanks soldsold, of course its more than i guestimated (but only a little bit) are you happy with it?

justflow1983

Two comments:

1) check out sheepswool if you're looking at cellulose. The thermal conductivity is similar and sometimes its cheaper. I've been told it deals with moisture much better as well.

2) see if you can go to 600mm centres on your studs. with 140mm studs, 600 centres should be more than enough, and you will have less thermal breaks in your wall. This will greatly improve its performance... do a web search for "Advance Framing" or go to www.buildingscience.com to see what I mean. They don't really use natural insulants in North America, but the principles of the framing and construction are the same.

tfer

thanks just flow, have been thinking about 600mm centers with a rigid insulation covering all, eliminating thermal bridging, horizontal battens @ 400 centers for a service cavity and then slab, if I did this where would the VCL go? in front of the rigid insulation or behind?

justflow1983

PM sent

justflow1983

VCL always goes to the interior of any insulation, so that moisture in the assembly can migrate out. I'm not sure where you're saying the rigid insulation goes, a good example of how to insulate timber frame is here:
http://www.buildingscience.com/documents/designs-that-work/information-sheet-boston-profile/?topic=/doctypes/designs-that-work

soldsold

tfer - job is not done yet so I cant say if Im happy with it, but by what Ive read it seems to keep the people happy who have it installed.

The 14 euro price I quoted is for pumping only, between gutex softboard outside the rafters and OSB inside. Would be about 4 euro per m2 more if parpac membrane needs to be put up first.

Im definitely happy with the softboard if anyone is considering using it, the roof is not complete yet but Im very impressed with it so far.

Regarding 600mm centres - this can make the roofing battens bouncy when nailing the slates (according to my roofer and some posts I have read) but the softboard eliminates this bounce. Also, if you are putting in velux windows be aware that the rafters have to be doubled up, and depending on the velux positioning, this can mean that extra rafters start appearing everywhere. I tried to have 2 velux within the same rafters where possible, eg an upstairs velux window high in the roof and a velux below it near the eaves to let light into downstairs rooms. The doubled up rafters can then be used to support both velux windows.

tfer

thanks sold sold, I have no problems with the timber frame as i have been framing for over 20 years, stick frame and factory, what i need help with is the heating system and insulation. I think im going with sheep wool but for the heating ?

justflow1983

tfer, make sure you double check the U-value you're getting between sheepswool and cellulose. I think they're be similar, and I work in a sheepswool insulated building that is plenty warm, but its still a good idea to take a look. As a product, its ease of installation and moisture resistance make it better than cellulose.

With timber frame, you have a different set of heating conditions than a typical masonry house. Radiators are fine of course, they are used in both masonry and timber buildings effectively. But because you have very little thermal mass, a timber house will cool down relatively quickly after each heating cycle. The upside is you add less heat at each cycle and it escapes more slowly. If you want a quick reacting system, and you're using an HRV, you could always add a forced air heater to the same ducts as the HRV and have your heat that way like they do in North America. The other alternative is radiant floors, which are cast in concrete so you end up getting a lot of thermal mass and a house that retains heat like a masonry house would, with the advantages of timber frame. The downside is that, if you walk into a cold house after a week away, it won't warm up immediately as it takes a while for the heat to work its way out of the concrete. The slab can be poured over an OSB subfloor, no need for any other materials.

tfer

Thanks justflow, I called the bloke that did the BER on my house,( i just sold it this week) and we set up a meeting next week so will keep you posted on the result of that, this guy is big into energy efficiency

soldsold

Hi Tfer,

I just realised you have 140mm studs, my price of 14 euro was to fill 225 studs so 140 should be a bit less, although my quote was from a guy very close to me so would be a handy job for him and this probably means the price he quoted me is good, and he doesnt have to install parpac membrane

S

tfer

thanks for that soldsold, its amazing how my ideas keep changing from reading posts, now I think I will go for the 225mm stud @ 600mm cts. I'm still leaning towards the sheepswool, and today I saw an ad for asphalt shingles which I've used many times in the states and loved the system. 12.5 mm ply over the rafters, roofing felt and shingle, have never seen them used here but looks just like slates from a distance. the cost of the shingles were €10 sqm. ( its just another thing to add to the confusion in my head )

justflow1983

A word on stud sizes. In my mind, I wouldn't want to go further than 200mm in stud thickness, and then I'd make up the difference using 50-100mm rigid poly insulation or woodfibre softboard like Gutex makes. I have 3 reasons:

1) the rigid insulation acts as a sleave that covers the thermal bridge of the stud, giving you a tighter thermal envelope

2) 150-200mm studs are cheaper than 225, and you don't really need the extra stud depth for structure (even 90mm is big enough structurally to hold a house up at 400 centres). Also, the bigger the stud section, the more likely it is that you are sourcing it from an older tree, which is less likely to be sustainably harvested.

3) A thick layer of insulation board protecting your studs will mean that dewpoint condensation will occur there instead of inside your timber frames, avoiding dampness problems.

There are a lot of ways to do this sort of thing, but no matter what you go with its always important to look at a wall assembly holistically as an assembly. TF has a lot of layers and its best to make sure you are aware of how they interact.

In terms of Asphalt shingles, from a green perspective they're kind of nasty. They are energy intensive and polluting to make, and have a 3rd the lifespan of slates. Still, its your choice, I tend to worry a lot more about that kind of thing than most do.