Improving a cheaper frame.

[Russell griffiths]

So just wanted to find out anybody's experiences with taking a fairly standard mass builder spec timber frame and upping the spec. 

I was thinking that a lot of the standard spec frames use 147mm studs filled with various types of insulation with a cheap house wrap on the outside. 

My thoughts were to add additional insulation on the outside, as well as insulating the service area on the inside, then using one of the top grade airtight membranes as well as the addition of a suitable all singing all dancing rainsreen on the outside. 

The thing I'm wondering is the time I do this would I have been better of paying for a passive spec frame in the first place. 

Cheers russ. 

[ProDave]

I did look at this myself. I made the "mistake" of mentioning to one of the big TF companies up here about taking their standard product and adding to the insulation and air tightness.  As soon as i mentioned than, they refused to quote me, saying "there is no synergy between what we offer and what you want"

 

I am sure it is doable, just don't mention to the TF supplier this is what you intend.

 

i am not sure how you would be with building control. Normally the TF company produce all the drawings for BC. You would be deviating from that and it would be interesting to see how BC deal with that.

 

It may not be as simple as you think. My house in the end was properly designed by an architectural technician, and in order to mitigate condensation risks in the frame, the OSB racking layer is on the inside (I lost count of how many people told me I had put my frame up inside out) I am not sure how well a standard TF wold behave just wrapped in extra insulation.
 

[Russell griffiths]

Thanks for the reply Dave,I was just reading your blog. 

I built our previous house in 2006 and did it completely on site stick frame style and have considered doing it that way again, the reason for getting a company to do the frame was to speed the process up as the last one took weeks wielding the nail gun. 

At the moment I'm struggling to comprehend why every thing seems so sodding awkward when it needn't be. 

Plenty of more random questions coming, 

cheers russ. 

[Declan52]

Could you use an architect to do the full drawings for BC showing the extra insulation on the inside and outside so the timber frame company only build what would be a standard frame as normal. 

Don't see why you can't use the likes of the  wood fibre boards Dave has used for the outside and then fully fill the frame with a high spec insulation and then put another 50/80/100mm pir board on the inside. 

 

[ProDave]

Can you do what I did, get a local building firm to make and erect the frame? It's relatively common for small builders or joiners to make and erect a frame up here. Then you would get the frame built as you want it. Mine is a 190mm frame with 100mm of wood fibre board on the outside and the entire frame filled with Frametherm 35. Same for the roof as well, using the wood fibre board as the sarking board.  The "odd" bit being the OSB is then on the inside of the frame.  Also, because there is no brick or block outer skin, the Structural engineer specified that some walls must be covered in two layers of OSB to give sufficient racking strength.
 

[Crofter]

'ang on Dave, you've out your frame up inside out, haven't you?

(Sorry!)

 

Seriously, though, this highlights the basic principle of vapour control- the wall buildup should get more permeable as you move outwards. So really it is everyone else who has their frame inside out.

On my build, the PIR is on the inside of the frame, so whilst I haven't had any professional input on this I am happy that it will not be a condensation risk.

[Russell griffiths]

4 hours ago, ProDave said:

Can you do what I did, get a local building firm to make and erect the frame? It's relatively common for small builders or joiners to make and erect a frame up here. Then you would get the frame built as you want it. Mine is a 190mm frame with 100mm of wood fibre board on the outside and the entire frame filled with Frametherm 35. Same for the roof as well, using the wood fibre board as the sarking board.  The "odd" bit being the OSB is then on the inside of the frame.  Also, because there is no brick or block outer skin, the Structural engineer specified that some walls must be covered in two layers of OSB to give sufficient racking strength.
 

So if I was to go down Daves route, can you tell me who did the design of the frame and who designed the insulation side of things and also the condensation risk,

i think I have a problem coming up,I have an architect who I like very much as he has come up with some very valid points that I hadn't thought of, the problem comes as I don't believe he is going to be up to speed with the timber structure design or some of the newer thoughts regarding insulation and air tightness. 

Oh well another hurdle to get over. 

Russ. 

[Russell griffiths]

So sitting here thinking between the cold meat and leftover Christmas pudding,

pro dave mentioned that when he told TF companies he planned to add extras to there frame they weren't interested in supplying. 

So if you were buying a frame and going to have a large cavity and a brick skin and put further insulation in the cavity I'm sure they would be happy with this, so what's the problem if you want to screw it to the face and then clad With something else. 

[Crofter]

You'd have to amend your building warrant submission to include the additional insulation, and they might come back to you requesting a condensation risk analysis, maybe? Probably not a big hurdle at all to be honest.

[ProDave]

There is noting unique about my type of build, though it is not yet common in the UK.

 

This is the wood fibre board to cover the outside of the frame http://www.ecomerchant.co.uk/walls/insulation/ecomerchant-protect-ewi/steico-protect.html I actually used the Pavatex 100mm thick board rather than Steico, because my builder could get a better price on the pavatex, but they are essentially the same.

 

And this is is the sort of render system that goes on it http://www.ecomerchant.co.uk/walls/insulation/ecomerchant-protect-ewi/steico-protect-system-wood-fibre-board-lime-render.html Again I used the Baumit.com render as that was available locally at a better price, and was what my renderer was familliar with.

 

I have attached the vapor risk assesment done by my designer. It shows no vapour risk and also shows a long thermal time lag so the risk of overheating on a hot day is low.

 

u-wert-berechnung (10).pdf

 

With this information, there is no reason your architect cannot take on board what will be to him new ideas, and design your house using that sort of construction method.

 

In my case thy also employed a structural engineer to specify things like beam sizes for the roof, racking strength calculations etc and foundation design.

 

[Stones]

Our last house was built using the Supawall system.  140mm frame OSB on inner and outer face, injection filled with PU.  VCL onto inner face, battens then plasterboard.  Outface of OSB clad with breather membrane then 50mm PU which covered soleplate.  100mm cavity between timber frame and outer block skin to account for 50mm additional PU fitted to outer face of frame.  Helical wall ties required to tie TF to block wall.  No issues with condensation risk analysis.  

 

I believe some SIPS manufacturers are now saying you can fit additional PU onto the outer face of the panel.  Given that it has and is being done, it should simply be a case of running your proposed build up through a condensation risk analysis.