Sap calcs advise

[Mike_scotland]

We got our u values back.... thoughts?

 

Walls 0.22 (i think quite poor sounding)

 

Ground - 0.15

 

0.14 exposed floor??

 

0.12 -  roof

 

Any thoughts? Sound ok bar the walls.

Edited March 12, 2021 by Mike_scotland

[Moonshine]

walls and floors aren't great, what are the constructions?

[ProDave]

My memory is poor who is doing what, but was it you proposing a 100mm timber frame?

[Mike_scotland]

Im not 100% sure yet its a TF definitely.

 

What is the exposed floor meaning?

 

TF with blockwork and render is think its 140mm of wool.

 

Slab is 100mm pir below and 50 above. all relatively new to me so looking for advice.

[Mike_scotland]

  On 12/03/2021 at 16:35, Moonshine said:

walls and floors aren't great, what are the constructions?

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I didn't think it was that good.  What is a gppd raring for floor?

[Moonshine]

  On 12/03/2021 at 17:16, Mike_scotland said:

I didn't think it was that good.  What is a gppd raring for floor?

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It depends what you are going for, mine are as follows and currently at SAP (87 / B) based on the design, though there are many other things that effect your SAP rating.

 

External walls (masonry cavity) - 0.18

Suspended floors - 0.12

Flat roof - 0.11

 

My walls are the weakest point, but i think are a good balance of performance and price

 

Exterior full fill dritherm 150mm cavity wall - FSAP.pdfFetching info...

 

Blocks are £0.99 + vat each, and the insulation is about £9.20 / m², so in terms of materials its about £30 / m². bricklaying is about £22 / m² per 100mm wall leaf.

 

Render about £30 / m², and dot and dab plasterboard skimmed ~£8 / m².

 

So its about £110 per m² exterior wall (not including lintels etc).

 

 

 

 

 

[Mike_scotland]

  On 12/03/2021 at 16:35, Moonshine said:

 

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Yeh i get it,

 

We are going ASHP so want good insulation, we are coming in at 82B i think it is for SAP rating.

 

83Bfor environment.

 

So for clarity if we put more insulation in it would perhaps be a 85B or such like?

 

 

I have seen in one of the recommendations if we got a wind turbine it would increase us to 98A haha!

 

[Timedout]

The walls are not good enough. I doubt that would satisfy your technical standards in Scotland. If you really are using a 100mm timber frame you will need to internally insulate. Typical solution would be a contiguous layer of foil faced PU/PIR board like Kingspan over the inner face of the studs, all joins and junctions sealed and taped, counter battens, plasterboard. With only 100mm frame you are going to need a thick pu board, at a guess in excess of 75mm. The knock-on is making provision you set noggins and extra support for confers in the right places to pick up the plasterboard edges.

I am not making this up. I have done it already but I had a 140mm frame. My largest u values were a lot better and I achieved SAP A rate in practice.
 

Redesign now and aim for 0.1  u value for every element.

 

 

[Buzz]

@Mike_scotland is that EPS or PIR in the floor .

 

[Mike_scotland]

145 i think it is 

Panels inc OSB to G/F

Spandrel Panels inc OSB to F/F

Panels inc OSB to F/F

145x45mm C16 solepate, headbinder etc

140 Frametherm 32 in ext walls

Window stops / cavity closers

Mid floor joists, assumed JJI's

150mm wool between joists

150 PIR Insulation between rafters

20 PIR Insulation over rafters

420mm in 2 layers over flat ceiling at F/F level

22mm V313 chipboard flooring to F/F

Roof trusses

19mm Sarking to trusses

[A_L]

  On 12/03/2021 at 16:32, Mike_scotland said:

Ground - 0.15

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You have previously said the ground floor is 19m x 7.5m and I gave a U-value 0f 0.11 for 150mm PIR. What is the thickness and type of the insulation?

 

  On 12/03/2021 at 16:32, Mike_scotland said:

0.14 exposed floor??

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Do you have a floor on the first floor which has outside environment below it? Is some of your ground floor suspended and some 'slab on ground'?

 

  On 12/03/2021 at 16:32, Mike_scotland said:

Walls 0.22 (i think quite poor sounding)

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Here is a simulation below. So about right. As I said before you should add about 100mm of same insulation or equivalent to get about 0.13. The roof is O.K.

 

 

 

[Mike_scotland]

  On 12/03/2021 at 18:31, A_L said:

You have previously said the ground floor is 19m x 7.5m and I gave a U-value 0f 0.11 for 150mm PIR. What is the thickness and type of the insulation?

 

Do you have a floor on the first floor which has outside environment below it? Is some of your ground floor suspended and some 'slab on ground'?

 

 

Here is a simulation below. So about right. As I said before you should add about 100mm of same insulation or equivalent to get about 0.13. The roof is O.K.

 

 

 

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The outside enviroment area, could be the above the attached garage.

 

Its something lile that downstairs in size.

[Mike_scotland]

See these

[Moonshine]

  On 12/03/2021 at 17:46, Mike_scotland said:

 

We are going ASHP so want good insulation, we are coming in at 82B i think it is for SAP

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It can depend what ASHPs you are using using a recent model ecodan 11.5kw bum0ped my SAP rating up by 2 points

[Moonshine]

  On 12/03/2021 at 18:41, Mike_scotland said:

 

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The assessor has you using dense block on the exterior skin. Is that really required. If you use a 7N lightweight block then the thermal conductivity falls to 0.45 (e.g besblock ultralite) which will help a bit.

How about putting 25-50mm internally to the timber stud? With 50mm I think it would get it down to 0.17 IIRC

[Mike_scotland]

  On 12/03/2021 at 19:15, Moonshine said:

 

It can depend what ASHPs you are using using a recent model ecodan 11.5kw bum0ped my SAP rating up by 2 points

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I think its a nibe

[A_L]

@Mike_scotland, The floor only has 110mm of insulation not 150mm and is correct. Also because layer 4 is next to a ventilated airspace its thermal resistance should be disregarded, a small additional thermal resistance, 0.29m²K/W can be added to allow for a thicker external resistance layer because of lower air velocities. This would be quite significant.

Edited March 12, 2021 by A_L
to add 'can be added'

[Mike_scotland]

  On 12/03/2021 at 20:00, A_L said:

@Mike_scotland, The floor only has 110mm of insulation not 150mm and is correct. Also because layer 4 is next to a ventilated airspace its thermal resistance should be disregarded, a small additional thermal resistance, 0.29m²K/W to allow for a thicker external resistance layer because of lower air velocities. This would be quite significant.

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How do you mean? Would it help the sap or make it worse?

[A_L]

  On 12/03/2021 at 20:05, Mike_scotland said:

How do you mean? Would it help the sap or make it worse?

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Removing layer four would increase the U value and in theory make the SAP score worse but in practice may be to small to actually affect it. 

[Mike_scotland]

I think i need a sit down with the builder and the architect, i told them i want a good insulated house.

 

The ASHP wont be very effective if insulation so crap.

[A_L]

  On 12/03/2021 at 20:12, Mike_scotland said:

The ASHP wont be very effective if insulation so crap.

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If you can reduce the U value of the walls to the levels I have suggested then the insulation is reasonable. The major consideration after this is the air infiltration rate (draughts). At levels 'in tune' with the insulation levels the house could be heated perfectly well with an ASHP.

[Mike_scotland]

  On 12/03/2021 at 20:41, A_L said:

If you can reduce the U value of the walls to the levels I have suggested then the insulation is reasonable. The major consideration after this is the air infiltration rate (draughts). At levels 'in tune' with the insulation levels the house could be heated perfectly well with an ASHP.

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Do you reckon add another 100mm of wool insulation to the walls?

 

 

Or whats your suggestion? 

 

Is it floor and walls that need looked at?

 

The roof is 0.12 but its a 1.5 storey sort of thing so that will be our walls upstairs.

 

[Thorfun]

  On 12/03/2021 at 21:06, Mike_scotland said:

Do you reckon add another 100mm of wool insulation to the walls?

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50mm of PIR will reduce U-values substantially without taking up an extra 50mm of room size. 

[A_L]

  On 12/03/2021 at 21:06, Mike_scotland said:

Do you reckon add another 100mm of wool insulation to the walls?

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Yes, or another insulation to the same effect, it should cover the timber studs to reduce the thermal bridging effect of heat being transferred through the timber.

 

  On 12/03/2021 at 21:06, Mike_scotland said:

Is it floor and walls that need looked at?

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The walls have been dealt with above, the floor is O.K.(ish) but re-visit what I said previously what I said about having it in one layer.

 

  On 12/03/2021 at 21:06, Mike_scotland said:

The roof is 0.12 but its a 1.5 storey sort of thing so that will be our walls upstairs.

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Have all/any of the horizontal and sloping ceilings and vertical walls all been considered?

[Mike_scotland]

The horiztonal part is to be 420mm(420mm in 2 layers over flat ceiling at F/F level) of wool i think and the sloping part is 150 PIR Insulation between rafters 20 PIR Insulation over rafters.