Attic & roof insulation spec

mrsWhippy

Hi,
What are your views on the following spec suggested to us for our attic/roof instulation please?

*Attic insulation - 150mm Rockwool Rollbatt between ceiling joists with 100mm Rockwool Roll over. Form raised walkway and platform for water storage tank and maintenance

*Warm roof sloped sections - 120mm Quinn-Therm Easi-Dorm/ Quinn-Therm QW friction- fitted between rafters with 60mm Quinn-Therm QL Kraft liner boards fixed across the rafters, with Pro-clima Intello-plus vapor control layer between.

Any advice much appreciated

PMBC

mrsWhippy wrote: »

Hi,
What are your views on the following spec suggested to us for our attic/roof instulation please?

*Attic insulation - 150mm Rockwool Rollbatt between ceiling joists with 100mm Rockwool Roll over. Form raised walkway and platform for water storage tank and maintenance

*Warm roof sloped sections - 120mm Quinn-Therm Easi-Dorm/ Quinn-Therm QW friction- fitted between rafters with 60mm Quinn-Therm QL Kraft liner boards fixed across the rafters, with Pro-clima Intello-plus vapor control layer between.

Any advice much appreciated

Not up to date with Building Regs xcpt that you need to achieve certain 'U' values either for each element of the design or for 'whole house'. I'm sure others can clarify.
Most impoertant is to provide ventilation.
You could ask your specifier to state compliance unless it is just an acquaintance in which case the manufacturers will be delighted to do so.

mrsWhippy

Thank you. This is the outline spec suggested by architect for our initial cost plan. No idea of u-values of that setup, though going for airtight house with HVAC installed (so that takes care of ventilation)

This aspect of the building regs (to be fair, most of them) confuse the bejaysus out of me.

PMBC

mrsWhippy wrote: »

Thank you. This is the outline spec suggested by architect for our initial cost plan. No idea of u-values of that setup, though going for airtight house with HVAC installed (so that takes care of ventilation)

This aspect of the building regs (to be fair, most of them) confuse the bejaysus out of me.

OK.
I don't have copy of the BR anymore, specifically the TDGs. The spec looks ok to me.
Might I suggest that you ask your architect to confirm compliance with that element and indeed all parts of his design. Since you are saying architect, check that he is a registered architect. Also ask him is this the best value product. I have no vested interest here except to say I knew of technicians who called themselves architects. I have no problem with anyone providing a service technicians/draughtsmen, engineers etc. provided they declare themselves openly. A good friend was charged a fortune by a tech masquerading as an architect some years ago.

mrsWhippy

PMBC wrote: »

OK.
I don't have copy of the BR anymore, specifically the TDGs. The spec looks ok to me.
Might I suggest that you ask your architect to confirm compliance with that element and indeed all parts of his design. Since you are saying architect, check that he is a registered architect. Also ask him is this the best value product. I have no vested interest here except to say I knew of technicians who called themselves architects. I have no problem with anyone providing a service technicians/draughtsmen, engineers etc. provided they declare themselves openly. A good friend was charged a fortune by a tech masquerading as an architect some years ago.

Cheers, but our architect is trusted and registered and above board. We have been working with him for 2 years now. I guess I just want to ensure this spec meets up to date building standards for a well insulated, airtight house. Just looking for a second opinion really - since its my house, I need to do due diligance on all aspects of it (imo )

PMBC

mrsWhippy wrote: »

Cheers, but our architect is trusted and registered and above board. We have been working with him for 2 years now. I guess I just want to ensure this spec meets up to date building standards for a well insulated, airtight house. Just looking for a second opinion really - since its my house, I need to do due diligance on all aspects of it (imo )

Sounds like you are on the right road. You could call manufacturers, Quinn, and ask that question. I'm sure if higher spec/standard was needed they would be more than willing to tell you.
Sorry I cant be of any more help and best of luck.

mrsWhippy

Looks like that combo of rockwool will give u-value of 0.17 ...

delfagio

mrsWhippy wrote:

Looks like that combo of rockwool will give u-value of 0.17 ...

I could be wrong here as I cannot quite remember off hand now but I think the u-value you need from you attic is 0.16,

Maybe just check it out in the regs in Part L section

mrsWhippy

delfagio wrote: »

I could be wrong here as I cannot quite remember off hand now but I think the u-value you need from you attic is 0.16,

Maybe just check it out in the regs in Part L section

That was the ceiling insulation value. There is also the warm roof, 120mm Quinn-Therm with 60mm Kraft liner boards across the top (:o)

I think that gives around 0.14 ... or 0.15. Are those values then combined somehow?

Also looking at the cavity construction, we have a suggested 100mm 5N block outer leaf, 150mm platinum Eco-bead, 100mm inner leaf, 13mm sand/cement render + plaster coat. I think this gives us a u-value of 0.2. Would it generally be worth increasing the size of the cavity to 200 to increase that u-value to 0.15? Are there any extra expenses involved here other than longer ties and more insulation?

delfagio

The u-values are taken separate.

If you have slopes ceilings in rooms due to storey and half design or dormer design and you then also have the attic u value for the remainder.

Are you using the same insulation and finish on the attic as you are on the slopes ceilings in rooms??

If not, then the attic insulation may have to be increased.

Have you a BER assessor on board, it would be best to talk to one beforehand.

Regards the cavity wall build up, I can't really say much as it will depend structurally what is required. This is what could affect the cost, plus the additional insulation

mrsWhippy

Thanks Defalgio.

The Quinn-Therm insulation for the sloped sections is for a standard pitched attic roof - it's not a habitable room, for now anyway. The rockwool will go on that attic floor then ... does that make any more sense?

We have a BER assessor on board, we have some XML files from the DEAP. I must check actually what he specified for the roof values ...

Gumbo

Is this an attic conversion or a new dwelling?
Why are you isolating the roof space and asking for opinions on that?

What has the preliminary BER assessment stated and are you filling that or trying to achieve a better result?

mrsWhippy

kceire wrote: »

Is this an attic conversion or a new dwelling?
Why are you isolating the roof space and asking for opinions on that?

What has the preliminary BER assessment stated and are you filling that or trying to achieve a better result?

This is a new build. We just got the initial spec yesterday (5 pages) so am knee deep in u-values and cavity widths etc. We need to lock down the entire build fabric soon enough so the QS can proceed. So basically am looking for a second opinion on everything!

Btw BER assessment specified 0.13 for 'Pitched Roof -Insulated on ceiling' - that doesn't tell me anything :-/

sydthebeat

mrsWhippy wrote: »

Thank you. This is the outline spec suggested by architect for our initial cost plan. No idea of u-values of that setup, though going for airtight house with HVAC installed (so that takes care of ventilation)
.

mrsWhippy wrote: »

Btw BER assessment specified 0.13 for 'Pitched Roof -Insulated on ceiling' - that doesn't tell me anything :-/

surely the u values quoted in the BER assessment equate to the specification offered by the architect

otherwise both are pointless

and if they do equate together, then what is the query?
has the architect offered you two alternative specifications? or only one?

mrsWhippy

Sydthebeat, we only have one spec at the moment for which we have to provide feedback.

I'm assuming these specs meet the preliminary BER figures, waiting for confirmation on that.

The BER assessment was fairly conservative though (roof 0.13, walls 0.2, airtightness ), so I'm really looking at trying to improve these values and get the best build fabric we can for our money. I'm finding it hard to link the potential build cost with the u-values and then the energy payback so hard to know at this stage whether to just go with his suggestion as is, or push for better quality/more insulation. Thats why i'm asking for your feedback on the attic/roof spec. Is there something that we could replace it with to get better u-values for not much extra cost? Does Quinn-therm cause mould issues etc. Is a u-value of 0.13 for roof a bad goal to begin with?

Thanks

sydthebeat

some comments:

1. im not sure what comments you can provide when only offered one specification? As a minimum i provide 2 specifications to clients, one with MHRV and one without, as that seems to be peoples biggest economic choice when building a new dwelling... and the choice to go with or without has significant knock-on effects

2. walls at 0.2 are basic to be honest, (150 cavity pumped with bead)
my standard wall spec is 0.14, which is 150 full fill cavitytherm by xtratherm.... which is what id suggest before increasing the cavity with to 200+

3. quinntherm is basically the same as kingspan and xtratherm. Mould issues are not caused by the specific insulation per say, but by how the construction is put together... so its dependent on the construction details. Most construction products will have IAB or BBA certs with details on the correct way to install.

4. it sounds like the spec he is providing offers the bare minimum building regulation compliance. So before you think about upgrading any of the insulation, try to get a whole house cost of construction and see whether youve extra funds to play with.

Thatsnicenow

@Mrswhippy just wondering what ye decided on? In the same position myself!