Dew point

[curlewhouse]

On the old eBuild forum a very good point was raised about the fact that with SIPs your sole plate will be sitting on your foundation wall, so that will be where any moisture in the air condenses... and your wooden sole plate will be sat in the wet, with potential problems.

 

After a few conversations with my architect about this (and if you stop to think about it, it is a very good point) we are looking at something called Foamglass which is strong enough to build on. It will be interesting to see what our SIPs supplier's engineers and BC say as it could be an elegant solution, plus actually increase our insulation.

[jack]

I looked at this before we started looking at raft foundations.  I recall it being interesting stuff, but very expensive.  I think it's produced somewhere in Scandinavia.

[curlewhouse]

Yes, I haven't seen the price yet, but my architect did warn me it was expensive but that we'll only need one layer thank goodness.

Product details link HERE

Edited July 25, 2016 by curlewhouse

[oranjeboom]

I used Marmox Thermoblocks under my sole plate. Also ££ but I think may have been slightly cheaper. I did end up going to Belgium as local merchant (Jewson) messed me around with supply of the size I was after. Worth checking on lead times and don't believe anything your merchants tell you - go direct to manufacturer for confirmation on UK stock.

 

Blocks were easy to lay and nice and light to carry around. And should help protect the sole plate.

Edited August 5, 2016 by oranjeboom
photo

[K78]

On 25 July 2016 at 15:48, curlewhouse said:

Yes, I haven't seen the price yet, but my architect did warn me it was expensive but that we'll only need one layer thank goodness.

Product details link HERE

 

How thick is the required layer of foamglass? 

 

I was really interested in kingspan TEK sips before i started the thread on ebuild?

[IanR]

7 hours ago, K78 said:

 

How thick is the required layer of foamglass? 

 

I was really interested in kingspan TEK sips before i started the thread on ebuild?

 

What U Value are you targeting?

 

While foamglass is better insulating than other block work, it's not quite as good as EPS, so to achieve a Passive-slab type level of 0.1 U value for the floor and perimeter you'd need roughly 350mm foamglass.

 

But that's not the whole "issue" with SIPs. If you wish to eliminate cold bridging and condensation risk on the sole plate then you need an additional external layer of insulation that drops down passed the sole plate.

 

Where as on a thicker twin-stud wall or I-Joist wall there is an opportunity to place an EPS upstand under the middle of the sole plate so that the inner face of the wall is over the warm floor and the outer face is over a cold ring beam (or on the EPS upstand itself in the case of the twin-stud) and therefore braking the cold bridge, you can't do this with a SIP panel. Hence the need for EWI to isolate the sole plate from the cold side.

 

My experience is that SIP suppliers are much happier about additional insulation going on the inside than the outside, but I believe quite recently Kingspan have started to support EWI on their panels.

 

It's worth looking into the Potton PassivHaus that used Kingspan SIPs, their foundation was very complicated to resolve the cold bridging issues and IIRC they specified EWI to cover down passed the sole plate.

 

Seems to me there are easier solutions with twin-stud and I-Joist walls. Plus you get to use an insulation with better decrement delay and acoustic properties. 

Edited October 22, 2016 by IanR

[curlewhouse]

20 hours ago, K78 said:

 

How thick is the required layer of foamglass? 

 

I was really interested in kingspan TEK sips before i started the thread on ebuild?

It was literally 1 block thickness that was all.

 

13 hours ago, IanR said:

 

What U Value are you targeting?

 

While foamglass is better insulating than other block work, it's not quite as good as EPS, so to achieve a Passive-slab type level of 0.1 U value for the floor and perimeter you'd need roughly 350mm foamglass.

 

. 

 

1 layer of foamglass blocks that was all, like oranjebooms pics with the thermoblock (which we might substitute for the foamglass actually).

 

The foamglass isn't going under the internal slab, K103 is. We have a 50mm cavity then real stone outer.

Edited October 22, 2016 by curlewhouse

[K78]

I was reading a thread on another forum where it was suggested that a strip of 50mm EPS 150mm above and below the sole plate, solves the problem. 

 

 

[K78]

14 hours ago, IanR said:

 

What U Value are you targeting?

 

While foamglass is better insulating than other block work, it's not quite as good as EPS, so to achieve a Passive-slab type level of 0.1 U value for the floor and perimeter you'd need roughly 350mm foamglass.

 

But that's not the whole "issue" with SIPs. If you wish to eliminate cold bridging and condensation risk on the sole plate then you need an additional external layer of insulation that drops down passed the sole plate.

 

Where as on a thicker twin-stud wall or I-Joist wall there is an opportunity to place an EPS upstand under the middle of the sole plate so that the inner face of the wall is over the warm floor and the outer face is over a cold ring beam (or on the EPS upstand itself in the case of the twin-stud) and therefore braking the cold bridge, you can't do this with a SIP panel. Hence the need for EWI to isolate the sole plate from the cold side.

 

My experience is that SIP suppliers are much happier about additional insulation going on the inside than the outside, but I believe quite recently Kingspan have started to support EWI on their panels.

 

It's worth looking into the Potton PassivHaus that used Kingspan SIPs, their foundation was very complicated to resolve the cold bridging issues and IIRC they specified EWI to cover down passed the sole plate.

 

Seems to me there are easier solutions with twin-stud and I-Joist walls. Plus you get to use an insulation with better decrement delay and acoustic properties. 

My concern was with the condensation issue rather than a target u value. I want a warm comfortable house but I'm not looking for passive levels. 

 

One sip supplier sent me an article by Mark Brinkley regarding a 145mm sip house heated only by a wood burner and MVHR.

 

The big benefit for me with sips over timber frame is that I have a open plan layout with a vaulted ceiling. 

 

I did have a twin stud quote from MBC, but I found it expensive and they were slow to respond. I've not looked into I-joist at all yet, I'll take a look. 

 

My budget is tight as I'm building without a mortgage. I would consider a block build, but it seems difficult to get a quote in the same way as you can from a timberframe supplier. 

 

So it looks like a choice between basic timber frame or sips. 

 

[ProDave]

How about what I am doing? Timber frame with external (wood fibre) insulation board and render direct onto the wood fibre board.  A lot of this typer of build is possible DIY if you are on a tight budget.
 

[K78]

40 minutes ago, ProDave said:

How about what I am doing? Timber frame with external (wood fibre) insulation board and render direct onto the wood fibre board.  A lot of this typer of build is possible DIY if you are on a tight budget.
 

 

I like your approach. I may do something similar. My thinking is that if I timber or tile clad, I can DIY that with a joiner who I know. Render quotes have been really expensive. 

 

Timberframe quotes are coming in from £19k-£23k. Sips are £26k-£33k. MBC was just too expensive for me to consider. 

 

Edited October 22, 2016 by K78

[IanR]

1 hour ago, K78 said:

One sip supplier sent me an article by Mark Brinkley regarding a 145mm sip house heated only by a wood burner and MVHR.

 

The big benefit for me with sips over timber frame is that I have a open plan layout with a vaulted ceiling. 

 

I did have a twin stud quote from MBC, but I found it expensive and they were slow to respond. I've not looked into I-joist at all yet, I'll take a look. 

 

If it was 145 SIPs on its own then it was probably a large wood burner as the SIPs will just have met building regs.

 

I'm not sure of the benefit of SIPs for the open plan and vaulted ceilings. With large spans the required increase in timber fraction and cold bridging will drop the "real" performance of a SIP structure. With an I-Joist roof you just go for a deeper I-Joist for the large spans, no negative effect on performance.

 

You may not be comparing like-for-like on your quotes. It's unfair on MBC to compare their twin-stud costs to a 145mm SIP cost. You need to add another 95mm of EWI to the SIP price plus a whole load of air tight detailing. 

 

When I costed SIPS and twin-stud, for the same performance the price was equivalent, I-Joist was a little cheaper.

[K78]

17 minutes ago, IanR said:

 

If it was 145 SIPs on its own then it was probably a large wood burner as the SIPs will just have met building regs.

 

I'm not sure of the benefit of SIPs for the open plan and vaulted ceilings. With large spans the required increase in timber fraction and cold bridging will drop the "real" performance of a SIP structure. With an I-Joist roof you just go for a deeper I-Joist for the large spans, no negative effect on performance.

 

You may not be comparing like-for-like on your quotes. It's unfair on MBC to compare their twin-stud costs to a 145mm SIP cost. You need to add another 95mm of EWI to the SIP price plus a whole load of air tight detailing. 

 

When I costed SIPS and twin-stud, for the same performance the price was equivalent, I-Joist was a little cheaper.

I wasn't comparing like for like. MBC want £52k, which is more than twice the price of other timberframe quotes and significantly higher than sips. 

 

The benefit with sips for open plan and vaulted ceiling is cost. They come that way as standard.

 

I'm not a penny pincher  when I first started on this "journey" I had a "secure" job. Never thought a mortgage would be a problem. 

 

Touchwood homes are a fair distance from Manchester and I would imagine they have a lot of work on. I've not found any other companies offering I joist frames.   

 

If I do go for a 140mm timberframe or 150mm sip I will be adding additional internal insulation. 

 

[ProDave]

The MBC quote would probably have included the foundations which I will bet the other quotes don't include? and the insulation in the walls and roof.  I tried MBC but had a hickup so never actually got a quote, but my shell cost has turned out at roughly £500 per square metre which is on a par with what most people pay MBC so they look to me to be correctly priced.

 

A vaulted ceiling will require a ridge beam to support it and that is what I have used with my timber frame.

 

140mm timber frame is to small, I went for 195mm suplimented by the 100mm wood fibre external insulation as well.

 

I found Touchwood to be expensive but ovbiously not everyone finds that to be the case.

 

What I found in the end was rather than go to a specific package builder, I employed an architectural technician that understood low energy houses, to design it for me, and then a local firm of builders constructed and erected the frame to their design.  That approach can yield whatever you want, and I know there is a house half a mile from here being built entirely of I beam joists for floor walls and roof.
 

[K78]

38 minutes ago, ProDave said:

The MBC quote would probably have included the foundations which I will bet the other quotes don't include? and the insulation in the walls and roof.  I tried MBC but had a hickup so never actually got a quote, but my shell cost has turned out at roughly £500 per square metre which is on a par with what most people pay MBC so they look to me to be correctly priced.

 

A vaulted ceiling will require a ridge beam to support it and that is what I have used with my timber frame.

 

140mm timber frame is to small, I went for 195mm suplimented by the 100mm wood fibre external insulation as well.

 

I found Touchwood to be expensive but ovbiously not everyone finds that to be the case.

 

What I found in the end was rather than go to a specific package builder, I employed an architectural technician that understood low energy houses, to design it for me, and then a local firm of builders constructed and erected the frame to their design.  That approach can yield whatever you want, and I know there is a house half a mile from here being built entirely of I beam joists for floor walls and roof.
 

Just checked the MBC quote. £48k for the frame and £13k for the foundation. AFT were a lot cheaper for the foundation. 

 

I thought I'd have to use an insulated raft as the house will be situated close to a retaining wall. But my SE says the ground should be good enough for strip foundations. Hence my interest in foamglass. 

 

I wish i had a bigger budget. But at least I'll end up mortgage free. 

 

Since my original quotes, timber frame prices seem to have risen by 25% and sips have come down considerably. 

 

It it would be great to employ a architectural technician but I fear costs could spiral. At least with the TF/sip providers I get a set price. 

 

Edited October 22, 2016 by K78

[ProDave]

What I found with the "standard" timber frame kit suppliers, was as soon as you mentioned you wanted a really good air tight well insulated house, and you would supplement their standard package with extra insulation and air tightness detail, then they suddenly refused to quote. One said "there is no synergy between what we offer and what you want"
 

[K78]

1 hour ago, ProDave said:

What I found with the "standard" timber frame kit suppliers, was as soon as you mentioned you wanted a really good air tight well insulated house, and you would supplement their standard package with extra insulation and air tightness detail, then they suddenly refused to quote. One said "there is no synergy between what we offer and what you want"
 

 That's why I'm thinking SIPs might be a good middle ground.

 

They claim good air tightness and it would be easy and cheap to add DIY internal insulation. 

 

[ProDave]

But adding extra internal insulation will make the frame colder and may lead to condensation issues. That can be a problem with SIPS around the sole plate area.

 

The one thing I got by having mine designed properly was a proper thermal analysis of the whole wall make up :

 

Ignoring the fact it's in German, what you see is there is no condensation risk,  and it has a long decrement delay, so changes in outside temperature will only slowly affect inside temperature so the risk of overheating on a hot day is minimised.

 

you really want some similar analysis if you start adding insulation to a standard product.

 

 

u-wert-berechnung (10).pdf

[Crofter]

15 hours ago, ProDave said:

140mm timber frame is to small

 

I think that statement could be a bit misleading.

The OP has already said that he would be adding internal insulation as well.

Also, do you mean 'too small to pass building regs' or too small to meet some other standard?

And of course it depends on what type of insulation is inside that frame.

 

(Not having a go, but just wanted to point out that there are a lot of variables to consider).

[K78]

3 hours ago, ProDave said:

But adding extra internal insulation will make the frame colder and may lead to condensation issues. That can be a problem with SIPS around the sole plate area.

 

The one thing I got by having mine designed properly was a proper thermal analysis of the whole wall make up :

 

Ignoring the fact it's in German, what you see is there is no condensation risk,  and it has a long decrement delay, so changes in outside temperature will only slowly affect inside temperature so the risk of overheating on a hot day is minimised.

 

you really want some similar analysis if you start adding insulation to a standard product.

 

 

u-wert-berechnung (10).pdf

 

Kingspan have recommended specs for additional internal insulation.  I plan to add 50mm eps external insulation 150mm above and below the soleplate. With the soleplate sat on marmox blocks.

 

With my budget being so tight, I'm not sure it would be wise to put a lot of money into external insulation at this stage. I'm not in a position to spend money on something that will take 25 years to pay back to initial cost. 

 

I was really sold on solid masonry with external insulation until I priced external insulation render systems. 

 

Im going to look at the Marley eternity vertigo brackets because they look like a cheap simple DIY solution to ewi.....but I thought ewi was a cheap solution until I got a quote. 

[K78]

3 hours ago, Crofter said:

 

I think that statement could be a bit misleading.

The OP has already said that he would be adding internal insulation as well.

Also, do you mean 'too small to pass building regs' or too small to meet some other standard?

And of course it depends on what type of insulation is inside that frame.

 

(Not having a go, but just wanted to point out that there are a lot of variables to consider).

 I went to view a development of 4 timberframe houses that one of the local providers has built.

 

They are 140mm frame with a combination of render board and timber cladding on the outside. All passed building regs and sold within a couple of weeks. 

 

He said they scored a B on Epc but would have got A, if they had solar panels. 

[TerryE]

52 minutes ago, K78 said:

He said they scored a B on Epc but would have got A, if they had solar panels. 

 

Yup, we missed an A by one point because we use Electricity to heat our house and don't have PV. The fact that you only need ~15kWhr of base heating / day for an average December and we will be using a green tariff is irrelevant to the failing on the A rating.

 

[Stones]

Our last house was built using the Supawall system - a 140mm injection filled timber frame, with an additional 50mm kingspan fixed to the outer face of the frame (which covered the sole plate), 50mm cavity then block outer leaf.  We had to use hellical rather standard wall ties but otherwise no real difference in how the frame / outer leaf interacted.

[bissoejosh]

On 10/22/2016 at 02:11, IanR said:

Where as on a thicker twin-stud wall or I-Joist wall there is an opportunity to place an EPS upstand under the middle of the sole plate so that the inner face of the wall is over the warm floor and the outer face is over a cold ring beam (or on the EPS upstand itself in the case of the twin-stud) and therefore braking the cold bridge, you can't do this with a SIP panel. Hence the need for EWI to isolate the sole plate from the cold side.

 

Sorry I realize this is an old post but I'm looking into the sole plate issue myself and came across this thread. We're going for an i-Beam frame as mentioned but currently our sole plate is drawn as a 245mm solid timber - was yours an i-beam laid on its side and if so did you insulated the web? Apologies If I've misunderstood!

[IanR]

Mine is a solid sole plate. 

The Engineer for the insulated raft did show an I joist on its side for the sole plate, so I assume it can be done, but that's not how the TF supplier did it. 

While the thermal bridging would be further reduced with an I Joist sole plate, it would not give much flexibility with bolting positions to fix the sole plate. I believe most I Joists have a 47mm deep flange so your going to want the bolts right in the middle. Your Slab would then need to be spot on, assuming your having and EPS upstand coming up underneath the soleplate. 

 

A solid sole plate gives a little more flexibility. 

Edited October 22, 2017 by IanR