UFH in slab or screed, eps or pir insulation?

[joe90]

I ended up with UFH pipes in a 70mm screed, originally wanted them in a 100mm slab but an untimely illness screwed up my timescales. I am hoping 70mm will still act as a large enough buffer. This is over 200mm PIR.

[Nickfromwales]

10 hours ago, Ed Davies said:

 

Funny that, I got chucked off there for saying how bad the thread on Russ's fire was. (Long after the thread happened.)

Cant happen here you'll be glad to know. We have a structure which avoids SPoF and no individual can make any such decision on their own. The FMG ( made up of 17 staff / members ) get together and discuss it like grown ups, we discuss it, and it gets voted against, or for, if there are mixed opinions. You'd have to seriously piss us off before getting shown the door. Only one has earned such privilege to date IIRC. 

Enjoy!

[russ_fae_fyvie]

9 hours ago, joe90 said:

I ended up with UFH pipes in a 70mm screed, originally wanted them in a 100mm slab but an untimely illness screwed up my timescales. I am hoping 70mm will still act as a large enough buffer. This is over 200mm PIR.

Yeah thats what we had on the previous house (that seems to warrant blokes being banned on Navitron !!) and it was ok but cost wise having 70mm screed on top of the slab is just more money, we will be now going for 100mm slab (with UFH) and 200mm of Insulation, went to online calculator and although 300mm is even better I think we will just got for 200mm which is a compromise of cost and efficiency.

Fingers crossed !

[Nickfromwales]

6 minutes ago, russ_fae_fyvie said:

Yeah thats what we had on the previous house (that seems to warrant blokes being banned on Navitron !!) and it was ok but cost wise having 70mm screed on top of the slab is just more money, we will be now going for 100mm slab (with UFH) and 200mm of Insulation, went to online calculator and although 300mm is even better I think we will just got for 200mm which is a compromise of cost and efficiency.

Fingers crossed !

200mm of what though ? ? PIR or EPS?

[joe90]

Yup, 200 pir is close to 300 eps.

[A_L]

Just remember you need a VCL above and below PIR

 

http://blog.celotex.co.uk/technical/what-celotex-insulation-can-be-used-in-floor-applications/

[russ_fae_fyvie]

@Tin Soldier

@Alexphd1

Guys an unrelated question as you are local to me.

I've just had a new quote from the joiner who was going to erect the kit but he is now taking the pi55 !

Not sure if you guys used a joiner to erect your houses but wondered if you could recommend anyone local who might be interested in quoting for the build ?

cheers

[Alexphd1]

Sorry bud we have done everything oursleves inc making the roof trusses so I don't know anybody who I can recommend.

[ultramods]

50 minutes ago, russ_fae_fyvie said:

@Tin Soldier

@Alexphd1

Guys an unrelated question as you are local to me.

I've just had a new quote from the joiner who was going to erect the kit but he is now taking the pi55 !

Not sure if you guys used a joiner to erect your houses but wondered if you could recommend anyone local who might be interested in quoting for the build ?

cheers

 

You could try Craigmile Joinery in Inverurie. This is the company that will be erecting my timberframe in 3 weeks. They also do roofing and k-rend.

[Tin Soldier]

Russ when are you looking to erect the frame?

 

i can ask my joiner

[russ_fae_fyvie]

On 18/09/2018 at 22:26, Tin Soldier said:

Russ when are you looking to erect the frame?

 

i can ask my joiner

Probably in the Spring, would like to get founds down before the winter if we can but depends on weather and other 'things' !

If he's interested just ask him to get in touch or I can call him.

 

cheers

[oranjeboom]

On 18/09/2018 at 20:38, russ_fae_fyvie said:

@Tin Soldier

@Alexphd1

Guys an unrelated question as you are local to me.

I've just had a new quote from the joiner who was going to erect the kit but he is now taking the pi55 !

Not sure if you guys used a joiner to erect your houses but wondered if you could recommend anyone local who might be interested in quoting for the build ?

cheers

Did you say your kit is SIPs? Including the roof? Had my kit from a SIPs company who turned out totally incompetent and unprofessional (you didn't mention them here you will be glad to hear - and the mods will be happy to hear that I won't type their name in BIG CAPS here either!), but they sub-contracted the install out who sub-contracted that out to a couple of installers who actually did a great job. They will travel anywhere if you don't get anywhere.

 

Oh yes, and make 101% sure you get someone decent to pour your floors. I used some prick who was recommended by a local architect, but I'm still rectifying his utter bollox of a job now.

 

I'm sure you can't find anyone worse than that!

[russ_fae_fyvie]

It is but not from a SIPs company, they are all solid insulated panels, including the Vaulted Area of the roof. I did speak to a 'proper' SIPS company to get an alternative quote but they were more interested in telling me the 'other' company weren't as good as their kit, etc, etc, so that put me off the straight away !

This company are local (10 miles away) and have a good reputation locally, also the builder (founds, etc) and Joiner has worked with their kits (and me) before so hoping it all goes to plan.

The guy pouring the founds (and other groundwork) did our other Log House Foundations in 2009 so I know his work is good, hopefully this time too !

Of course you know what they say about the best laid plans !!

Edited September 22, 2018 by russ_fae_fyvie

[russ_fae_fyvie]

Well guys its been a while but today we poured the 100mm slab after fitting the Insulation and UFH Pipes, kit is due on site on 12th March so its all systems go now !

It was a bit dark on site tonight so I couldn't get a photo but there are now loads of others on the website, don't get too bored !!

 

www.stationbrae.uk  

 

Edited February 20, 2019 by russ_fae_fyvie

[scottishjohn]

On 13/08/2018 at 00:21, Nickfromwales said:

I like the sizes of the rooms and the layout,  but why the huge 'boiler room' and why don't you use some of that space to give yourself a shower ensuite ? Seems a strange use of that considerable floor space. 

 

Please do have a good read here about battery systems and their current longevity / RoI as there still seems a lot to discuss prior to investing a lot of capital into that endeavour. Nowt wrong with cabling for it in anticipation btw. ?

With that amount of PV you'll find there isn't that much left for battery charging, after DHW / driving a heat pump, plus plug in loads / general / self consumption etc, so look at what ( excess ) you can produce before looking at what electric-dependant equipment / devices you'll consider installing . 

I'd focus on DHW first, and then look at how you'll manage space heating eg an ASHP used in the day to heat up the slab and then just a Willis heater to maintain / top-up the overnight temp, if required. 

If your at or around PH standards you may well be ok to go all-electric and do away with the heat pump. 

has anybody gone for pure electric for heating house at passiv  level  and any info on result of that

If its a viable  choice then solar thermal for DHW  would be my choice as well

Edited February 21, 2019 by scottishjohn

[TerryE]

If you use pure electric then you will only ever get a CoP of 1.   Have a wet UFH laid very much as above in @russ_fae_fyvie's picture (see my blog).  At the moment we heat this electrically using a Willis heater in the heating loop and I have posted separately on this.  This is a cheap and very flexible arrangement.  I plan to add an ASHP in the summer, as the paybacks justify this cost if I do the installation myself ~£2K vs ~£6K (and just as I did the rest of the plumbing).

[russ_fae_fyvie]

Flooring and UFH now in, kit arrives on the 12th March !!

 

www.stationbrae.uk

Edited February 24, 2019 by russ_fae_fyvie

[OldSpot]

Just resurrecting this thread.

 

Couple of quick q's for those who maybe able to help:

 

1. Clearly a concrete slab has a lower thermal conductivity when compared to a liquid screed and combined with it being thinner SWMBO is a little nervous about a 100m slab with UFH due to the increased warm up times. Is it that bad and what sort of time are we talking about? My heatloss calcs suggest UFH works fine but will need a bit of supplemental heating in the coldest temp which is fine. We plan to have a wood burner anyway.

2. What sort of mix are you using for the slab? (Strength & type - self compacting?) Ours is just a simple floor slab - there are no walls etc built on it and we have 300mm of EPS under it, mainly because it was originally a suspended floor. For anyone think about us using just a screed above it has a ground bearing slab at the bottom....

 

When I read about the ground temp being a constant 8 or so degrees  I wondered if anyone has thought of putting a loop in the ground - similar to a GSHP to provide cooling during the summer....!?

 

 

 

 

[TerryE]

3 hours ago, OldSpot said:

We plan to have a wood burner anyway

 

Lots of history and debate on other threads about this topic; have a search.  Wood burners are highly problematic if you have a high energy spec house with MVHR.  A typical wood burner might have a minimum 4kW output and dumping this amount of heat into a single room can cause problems.   We have UFH which typically comes on overnight for however long needed to do the daily top-up.  Used to have wood stoves in our old farmhouse but don't miss them or the dirt or need to feed them in the new.  We don't have any heating on the top 2 floors, but do use a small oil-filled electrical heater on the first floor for a few hours top up overnight in the coldest months.

 

You need to be careful in designing out edge thermal bridging in your slab profile.

 

3 hours ago, OldSpot said:

When I read about the ground temp being a constant 8 or so degrees

 

An approximation. It averages to whatever your day-round year-round average temperature is in your locale.   In our case our slab is at ~22½°C year round and even with 300mm EPS, this heat is constantly bleeding into the ground under the slab, so I suspect that ours might be nearer 10°C.   

 

Edited November 18, 2020 by TerryE

[joe90]

6 hours ago, TerryE said:

Wood burners are highly problematic

I would prefer to say “could be problematic “. We have a house built to near passive spec and have a wood burner. It is room sealed and yes it’s probably a little bit of a heat sink in cold weather but the room in general is no colder than the rest of the house. We have MVHR (but still have not balanced it yet ?) if we light the stove fir a cosy evening the room goes up from 21 to 23 degrees after an hour, we don’t light it fir long and the house is noticeably warmer even the next morning (lots of thermal mass ?). We would not be without it.

[ProDave]

Another with a well functioning WBS in a well insulated sealed house with MVHR

 

My main point I constantly repeat is the stove is in the largest room, that opens with double doors to the stairwell and another set of double doors to the living room.  With all the doors open the stove gently heats the whole house rather than overheats a single room.

 

We did try an experiment and shut the doors with the stove going and yes that room quickly got too hot, but then quickly cooled down when you allowed the heat out to the rest of the house.

 

So just give careful thought to where you are going to put a stove so it has the ability to spread it's heat sensibly.

 

 

[mvincentd]

My ufh is in my structural slab which is 300mm thick in half its area and 200mm the rest.   It sits on 200/300mm xps accordingly, with 100mm up the sides.

I have 11 loops but have only used 3 as it seems to be all the house needs...we like cool bedrooms and towel rails warm bathrooms.

With the ufh coming on for 90 minutes at both 5am and 5pm the house  stays pretty steady....if we want a half degree boost from here it takes a good half hour to feel it (we put 32 degree water in).

 

[daiking]

Are there any instances on here where a UFH set-up has not been adequate for a high thermal standard build?

 

 

[TerryE]

6 hours ago, daiking said:

Are there any instances on here where a UFH set-up has not been adequate for a high thermal standard build

 

There can be a significant difference between as designed and as built (in practice) -- especially if you miss some major thermal bridging.  If your house is built to PH-class then a low temp UFH should be easily capable of adding sufficient heat in the depth of winter. 

 

Options like a supplemental electric oil rad or a WBS can allow you to optimise your design for the 4-5 transition months but still have a comfortable environment in the depth of winter.  In our case for example we have no heating on the top 3 floors and the bedroom temps get down to 19°C or so in Dec / Jan / Feb cold spells which is a bit cool for us.  Having a small electric rad on in my 1st floor study for a few hours overnight (with the door open) in these cold months brings this up to 21°C or so.  A lot cheaper than 1st floor UFH or wall rads, and the incremental running cost (we have E7) is negligible.