Insulation Spec for UFH

BMD

Can someone advise me on the following spec that my architect has spec'd for my UFH and insulation. I don't think it is sufficient

Ground Floor

Slab to be in-situ reinforced concrete slab in accordance with the Structural
Engineers details, incorporating insulation to achieve min 0.25 W/sq mK.
75mm Cement: sand screed to accommodate Under floor heating pipes on
100mm high density insulation on 150mm in situ Concrete floor slab.
Dpc to be lapped and bonded with “Monarflex RMB” 400 Radon membrane on
hardcore. Radon sumps to be fitted with pipes from same to terminate outside
building and be capped.
25 mm “Kingspan” Therma Floor TF70 insulation to perimeter of slab taken up
between wall and slab. Ground floor construction to achieve minimum of 0.25 W/sq. mK

First Floor

Concrete panel floor slabs
To be 150mm precast concrete panel floor slabs in accordance with IS and
structural engineers specifications with 75mm Cement: sand screed to
accommodate Under floor heating pipes

sinnerboy

The ground floor needs to achieve 0.15 U value .

This will require 120mm PIR or 200 EPS

The upper floor should have min 25 PIR between the UFH screed and the structure below . So the UFH screed can not be the structural screed .

We do not give structural advice here - so no more advice than the following will be posted

Sometimes a structural screed is not required . The PC slabs can be merely grouted . If the slabs do need a structural screed then you will need two screeds as follows - PS slabs - structural screed - insulation - UFH screed .

Not all PC slabs are the same and you must proceed only upon taking advice from a Structural Engineer .

AckwelFoley

You could see about giving the plans to an energy acessor.. They will be more familiar with u-values and means to acheive it

BMD

Thanks sinnerboy.
The rest of my specification (walls, roof) is spec'd for Kingspan products. What Kingspan product (and how many mm) would I need on the ground floor to meet the 0.15K specification for UFH?

Also, what would my equivalent kingspan spec be for upstairs?

I have read some conflicting arguments wrt to insulation on the first floor. Why is it required? To stop you heat going downstairs instead of up?

Finally, in the building regulations there is reference to ground floors and other exposed floors? What constitutes other exposed floors?

BMD

I've done a bit more reading since and I see that Kingspan Thermafloor TF70 is PIR. Based on their product information, 100mm of this product will only give me a U value of 0.17, therefore I guess this is why I need a minimum of 125mm as suggested by you?

I would still appreciate any comments re the 'exposed floor' and the requiremnt for insulation on the first floor

sydthebeat

BMD wrote: »

I would still appreciate any comments re the 'exposed floor' and the requiremnt for insulation on the first floor

an area that overhangs a lower area will have an "exposed floor".....

the requirement for insulation on the first floor has more to do with the responsiveness of your heating system, than the thermal storage in the floor slabs...

your first floor rooms will heat up quicker if the UFH throws the heat up rather than down.,...

BMD

Thanks Syd,

the only type of exposed floor I can think off would be a first floor room above a car port or something like that.

I take your point regarding the thermal responsiveness is good. The only downside might be that if you have heat on downstairs, you might hope it would heat upstairs slightly also but I guess it is a trade off between the two and hence only 25mm of PIR is required.

Any thoughts on my other insulation spec's would be helpful. I think they are ok as I have calculated the U values to be 0.2 (walls), 0.19 (attic) and 0.17 (vaulted ceiling)?

In general do you all think that building regulation specs are a high enough spec?

External Walls.
External walls to consist of 100mm concrete block inner leaf; 70mm
'Kingspan' Thermawall TW50 cavity insulation; 50mm clear cavity, to achieve
min. 0.27 W/Sq. m K, 100 mm concrete block external leaf with roughcast/wet dash. Outer leaf tied to inner leaf with stainless steel cavity
ties at 750 mm (maximum) centres horizontally and 450 mm (maximum)
centre vertically generally (but 225 mm vertical centres at movement joints
and jambs of opes) and in accordance with structural engineers details.
Vertical control joints in outer leaf generally at 6.0m centres.
Interior of all external walls to be drylined with 38mm Kingspan Thermawall
TW56, mechanically fixed and finished with a plaster skim.

Roof Insulation
All roofs To achieve minimum U-value of 0.20W/sq mK
a Vaulted ceiling in Living room
150mm 'Kingspan' Thermopitch TP10 insulation between rafters fixed with
proprietary clips, with 50mm 'Kingspan' Thermopitch TP10 insulation
attached to under side of rafters
b Attic
Attic to be Insulated with 250 mm of glass wool roll.
Insulation of a width appropriate to the joist spacing to be laid between the
joists and to finish over wall plate on external walls. All end joists to be close
butted. Maintain a minimum of 50mm Airspace between insulation and
sarking-felt at eaves, by way of ventilators. Cold water tank and pipes to be
separately insulated. Do not insulate under the cold water tank.

soldsold

sydthebeat wrote: »

the requirement for insulation on the first floor has more to do with the responsiveness of your heating system, than the thermal storage in the floor slabs...

Separating the upstairs UFH screed from the concrete slab ceiling will also help give a more soundproof ceiling.

sydthebeat

BMD, a minimum u value of 0.16 is require on a flat attic....
generally this is achieved by 300mm quilted insulation.

BMD

Thanks Syd,

So if I up my spec as follows would my house be considered to insulated to a high specification (if installed correctly)?

Ground Floor
125 mm of Kingspan Thermafoor TF70

First Floor
25 mm of Kingspan Thermafoor TF70

Walls
As per original spec

Flat Attic
Increase fiber glass wool to 300mm (and have it over the joists not just between)

Vaulted Ceiling
As per the original spec

sydthebeat

BMD, youd be slightly over the minimum regulations....

we are seeing that, the more your consider energy conservation, the more important other factors than insulation become...

that spec would have been considered high 5 years ago....
nowadays is slightly better than average..... more attention must be put to thermal bridge details and air tightness...

BMD

Thanks Syd,

It sounds like I should get my spec reviewed and changed by someone who is very knowledgeable/qualified in this area.

Would a BER assessor be the best person to consult regarding this and if so then how much would such a consultation typically cost?

beyondpassive

Hi BMD,

Building spec's set minimum standards, therefore are worst allowable specification. If you are building a house for yourself to live in, it is well worth making a few improvements. Most peoples first port of call for insulation is Foil faced polyisocanurate (PIR) and Phenolic. Manufacturers resitivity values are optimistic to the point of fiction. Added to this the practicalities of bangin in insulation, leaves many gaps and cold bridges. The biggest problem is the cold riser wall and cold inner leaf coupled with the cavity closer block. Looking at any of our recently built building reg standard one off houses in winter with a thermal imaging camera, you can see the plynth is red hot. 25mm phenolic is not enough to keep the slab warm and you will end up heating the path outside.

Its virtually impossible to fit PIR board down to the wallplate to ensure continuity of insulation.

Its a watershed time for building, where the techniques and materials that we used during the celtic tiger no longer deliver the levels of thermal stability and humidity we now expect, or more to the point, we cant pay 3k a year heating bills in our peak oil era.

Many Engineers and Architects are still specifying the same aul spec, just adding a bit of drylining or a an extra board inside the rafters. Many BER assessors have little practical knowledge of building, so mind how you go there

The spec I'm using, is 250mm cavity and EPS formwork raft or AAC block, for the roof Softboard and cellulose with a services cavity. It adds a bit to the cost but at least you have a building thats future proofed and comfortable.

dfader

Beyondpassive,
I am considering a wide (220mm) cavity for my two story build, thanks alot to your advice here, but am concerned about it structurally. Would like to visit one (a two story preferably) in the flesh being built some time and talk to an experienced builder doing it because all block layers I've mentioned it to have said 'never done one that wide before'. So if you or anyone else knows of one being done would be great if you could PM me the location if you dont mind me having a look.
I am based in the northwest but do be down in the midlands fairly often too.
Thanks.

beyondpassive

P.M sent.