Thorfun

Yeah, sorry. I didn’t make it very clear! Our basement will only be under half of the house and will be a music and games room so needs to be cosy. as it’s only under half the house I guess I’d need 2 x separate slabs. One for the house sitting on the ground and one for the basement as the one for the part of the house with no basement won’t be able to extend to the part over the basement. I hope that makes more sense!

We are planning a basement and I was initially looking at an insulated raft but can’t figure out how that would work with the basement underneath? I fully admit that I have a ton of reading and research to do for our self build but I think not asking how you’re planning to do it would be a wasted opportunity! ?

I'm in a similar place at the moment and this is an interesting thread topic for me. Anyone got any other comments to add to what's already been said? did your windows go in? thoughts/experiences of Gaulhofer? did you get anywhere with your investigations or decisions?

that actually now makes a lot of sense. thank you!

now I'm even more confused! but that same insulating effect will be twice as thick to get the same U-value, right?

ok, twice the price for half the thickness. I guess that makes sense.

actually, now I think about it, to get similar U-values I'll need double the thickness of eco insulation so the I need to double those prices so the Kingspan isn't actually as more expensive than I first thought. sorry. schoolboy newbie error! ?‍♂️

so, I've been looking further in to this, specifically with regard to prices to compare our different options and must be doing something wrong! it appears that the Kingspan K12 framing board is the most expensive insulation when priced per m2 and compared to hemp, wood fibre and loose cellulose (just for the product and not including installation). please tell me I'm wrong here. I thought the PIR insulation was cheaper than eco products? or am I being naive here and you're actually paying a premium for thin insulation (and thus thinner walls)? if this is the case then I think I'd rather lose space from my room size and buy a cheaper and more eco friendly product.

thanks Patrick for the response. all great information! I've not actually looked at the prices of this stuff yet. once I get the final dimensions of the external walls I'll put it all in a spreadsheet and calculate the cost differences between them all. I assume that with the blown cellulose there are 3rd party companies that will perform the work after a timber frame has been erected? or are you limited to a timber frame company that offers it as a solution?

I'm wondering if I can use flexible wood fibre between the timber frame and then the rigid wood fibre sheathing on the outside as further insulation and air tightness and attach the timber cladding to the sheathing? obviously, I'm only just starting on my journey so something like that might not actually be possible for various/numerous reasons!

this was an interesting read (https://www.ecomerchant.co.uk/news/insulation-materials-compared/) that someone posted in another thread. it seems that maybe wood fibre might be the way to go as it has a lower lambda value and decrement delay value. more research is required! ?

yep! I've read it which is why blown cellulose is on the list of considerations. ?

thanks for the great information and the 'twice the thickness' simplicity makes perfect sense. so, unless I want really thick walls hemp is not really the way to go is what I'm getting from the responses so far! I will definitely look in to mineral wool. cheers.

Hi Patrick. thanks for the response. I am considering blown in cellulose as a potential option as well although that's not something that I can fit myself. at least with hemp batts I can fit them myself and save some money (as well as do my bit for the planet). although I guess a counter argument to saving money by self-fitting is that the money I would save by using blown cellulose would pay for someone to do it for me! so much to research and I've only just started!

I was thinking about simply getting Hemp batts and fitting them between the stud work of the timber frame. on the Black Mountain website their NatuHemp product has the following U-values: THERMAL PERFORMANCE Thickness Thermal Resistance (R) U Value 50mm 1.28 m2k/W 0.76 W/m2K 75mm 1.92 m2k/W 0.52 W/m2K 100mm 2.56 m2k/W 0.39 W/m2K 150mm 3.85 m2k/W 0.26 W/m2K 200mm 5.13 m2k/W 0.20 W/m2K 250mm 6.14 m2k/W 0.16 W/m2K interestingly, according to the Kingspan U-value calculator 120mm of their K12 framing board with the following build-up yields a 0.23 W/m2K U-value so similar to the 150mm of hemp. And both require further insulation to get to a decent U-value. Construction build-up includes: 3mm skim coated 15mm plasterboard Polythene vapour control layer Kingspan Kooltherm K12 Framing Board between timber studs 9mm OSB Kingspan nilvent breathable membrane Timber cladding on battens. I need to do a LOT more research on the whole subject and would value other opinions on the subject.

Hi Dave. thanks for the information on the Earthwool. I'll look in to that. I know that hemp isn't the best insulator. The Thermafleece Natrahemp product has a Thermal conductivity of 0.040 whereas PIR seems to have a thermal conductivity of around 0.023, hence the thick walls to get a similar level of insulation. some of our sustainability requirements will need to be dropped as we price up the build and it may end up being insulation but I'd like to at least investigate all options before we make a decision!

Hi all, we're currently in the plan drawing phase with the architect for our West Sussex project. We're trying to get away from using oil based products in the build and I am drawn towards using hemp for the insulation of the house. The architect has said that the calculations to get wall U values of around 0.15 with hemp we would need at least 400mm thick walls. We'd rather not lose that much internal space if possible so we're investigating a potential hybrid solution where we use hemp in the timber frame walls and then cover it in another insulation to obtain the required levels. he has suggested we look at the Actis products. I remember reading about the debunked claims on their old product (and have read through old threads on here about the multi-foil insulation) and am a bit sceptical but by using it as a secondary layer and it being so easy to fit that I could do it myself is quite a tempting solution. so, I guess my question to the forum is has anyone used hemp as an insulation material? can anyone think of a different (preferably non-oil based product) that could be used as a secondary layer to reduce the cold-bridging from the timber frame that isn't Actis? or can anyone suggest that Actis have got their act together and now have a product that is worth using? he was talking about the hcontrol hybrid Actic product with the built in vapour control. thanks in advance.

thanks for this. I'll take a look at his blog. I have a lot of reading to do. ?

thanks guys. feeling the love already. ?

Hi all, about 4 years ago we found a property ripe for demolish and rebuild. while we were on holiday we were gazumped on that property! ? then we found another property (a barn for conversion) that was going to be perfect. after 2 years of trying to sort out access over a 3rd-parties land and various other legal issues the sellers decided to pull out of the sale. ? not letting the b*****ds get us down we continued to look and have now found and completed on a rundown 70s bungalow that has permission for a replacement dwelling on a plot of just under 1 acre. ? we're currently working with an architect to draw up the plans we want for the house and then have the whole planning process to go through and then maybe in about 18 months we'll have a finished house but, for now, we're really excited about this upcoming journey our family will be going on. I wanted to introduce myself and I look forward to being part of this self-build community. cheers, Tom.