insulation levels for heat recovery ventilation system

N

new2building

Guest
Hi there,
We are in the process of picking our builder for our new build. We have been going around in circles trying to choose a heating system. After much googling and reading threads on this website we are thinking of going with :
UFH downstairs, rads upstairs (UFH in bathroom upstairs and one ensuite), oil boiler and buffer tank and heat recovery system.

I am wondering what are the steps involved in putting in a heat recovery system. How do you know if the house will benefit from it...

The house size is 2,700 sq feet. It will be a block build.

The insulation/block work the builder is quoting us for is as follows:
-150mm thick hardcore under floor slab
-100 mm thick concrete in ground floor slab
-300mm thick external cavity walls made uo of 100mm thick solid concrete block leaves with 100mm wide cavity with 60mm thick Kingspan Thermawall TW50 cavity insulation
-internal insulating slabs on all external walls
-12.5 mm thick plasterboard and skim to underside of ceiling joists
-150 mm thick fibreglass quilt insulation laid between ceiling joists in roof space
-150mm thick fibreglass quilt insulation laid on last over ceiling joists in roof space
- we are having block walls throughout the upstairs rooms and a conrete floor upstairs also

The quote is very detailed(about 10 pages) so I have just picked out the main points.
I know this topic has been discussed many times on this website. We would really appreciate if anyone has any opinions on whether we are doing the right thing regards our heating system. We were going to go geothermal/air-water but we are thinking maybe its better to put our money into the HRV instead. Does our insulation seem enough ?
We have been quoted for double glazed windows but are thinking we will upgrade to triple if it will help us.

Thanks for taking the time to read this ...any advice welcomed...we are both completely new to this process !!
 
What you need to do is get a BER assessor and tell them that you will need an in-depth service from them. Then get them to calculate the BER of this spec, and then modify it by changing insulation in roof space, in walls, under floor etc.

Your insulation seems to be under-spec'ed relative to anything else at the moment. Insulation (and draught proofing/air tightness) is generally the cheapest, most fool proof method of reducing your energy usage and getting most bang for each buck spent. Your spec seems to be min. spec at the moment.

HRV is a good option - but until the air tightness and insulation are in order, you are simply wasting money.
 

I agree, in fact I'd say your current proposals do not comply with current building regulation requirements. Please save yourself money and do not break the law by retaining professional advice.

Get a provisional BER and speak to your Certifier (Architect, Arch. Technician or Engineer)
IMO you should not use that Spec. - its so last decade! no offence!

HRV is worth consider, it will save money if the proposed house is well insulated and air tight. There are lots of threads on these topics. Good luck.
 
Thank you both so much for taking the time to reply to me. I suppose that was my question should I go to the HRV people and ask them if that is enough insulation or how do I find out?? So I will try to the route of the BER assessment people.
As I said I only took a few points out of the 10pages of the quote so I'm sure I left out alot of important things. Its just too long to quote it all here. Ill get a professional to look at it before I go down the route of spending alot of money on a system that may be a waste.

Another quote I have specifies (this time its a timberframe quote)
-100mm block external blockwork, 50mm timberframe, with 200mm fibreglass insulation and 52.5mm kooltherm k17 insulated plasterboard slab on inside of walls.
-All internal walls in timber stud insulated with rockwool for sound.
-Triple glazed windows and tegral slate roof storm proof barge 400mm fibreglas and 52.5mm k17 to flat ceiling at roof level.
-insulate floor level to achieve U value of 0.16

Do you think that is better?
I am being quoted 30k more for this quote than previous one...

Again thanks for taking the time to read this. I'm definitely going to get some professional advice...I need it!!!
 
new2building said:
As I said I only took a few points out of the 10pages of the quote so I'm sure I left out alot of important things. Its just too long to quote it all here.
Click to expand...

You are very welcome. I was refering to your 1st spec, IMO 60mm kingspan Thermawall TW50 cavity insulation is not enough wall insulation unless you can clarify the thickness of internal slabs on all external walls.

150mm thick fibreglass quilt insulation laid over ceiling joists in roof space is not enough! 300mm is more acceptable.

I definitely believe you need to speak to your Designer / Certifier and also organise a preliminary BER report.
Do your homework, it will save you lots of time, money and delays / grief!

The timber frame spec is better from the details supplier. It seems very expensive at 30K extra.
Maybe you should get 3 blockwork quotes & 3 quotes from 3 timberframe suppliers. Make sure you price like for like i.e you know exactly whats included in each quote.
 
Thanks again RKQ.
Have read quote again and the roof insulation is 300mm in the first quote. Yes we think 30k is too high for that second quote i mentioned, we do have another timberframe quote that comes in at the same price as the block built quote. We just have a good feeling about this builder but I am going to get onto the engineer that we are working with and get his opinion too. There is so much to do and so much to learn!!
 
I spotted the 150mm over 150mm quilted fibreglass insulation specification in your first post - this is a questionalbe detail/specification in my view, on several levels.

  • If there are any downlighters at that level, they will penetrate both the insulation and the vapour check - three is no way to avoid this although consequences can vary.
  • The depth of insulation will "bury" your services and make finding them hard but walking on them assidentally quite easy.
  • Quilted insulation will tend to compress over time, reducing its effectiveness - stuffing "more" in does not work!
  • Depending on the competence of the finishers it can place exposed water pipes and tanks at risk of freezing.
  • Unless a 50mm ventilation gap from the eaves is maintained, it can cause interstitial condensation in the attic space.
I think a better bet would to insulate between the rafters, carefully detailed to avoid the build up of interstial condensation per TGD F 2009.

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1647,en.pdf

Read Section 2, pp 26-28 Condensation in Roofs and look at Diagram 11. Sketch D for Rooms in the Roof.

Also you need to read the new Part L 2008 (Dwellings) Conservation of Fuel and Energy

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,19069,en.pdf

This allows for later attic conversion [assuming you upspec the attic "floor" joists now] and ensures all your services are maintained withing the warm envelope of the building.

I think you need to take professional advice.
You seem to be attempting to assess something that may well be beyond you to try and save money on professional fees.

At the bare minimum I advise people to get an architect for the general design and detailing of the house and an engineer to design the substructure and drainage, conduct a site assessment and address any road access problems.

If you want definitive advice on the insulation specification go to a BER assessor - there are many such around.

However you could also seek useful advice from a Mechanical and Electrical consulting engineer who deals with domestic work.

This will need to be paid for, but for writing you a compliant services specification as well it would be money well spent.

If you want a recommendation for such a firm I can offer it to you, and no, I don't work for them but have worked with them on projects and I've found them good.

It is important to note that while insulation gives most ban for your buck, a good MVHR system will help reduce costs in cold weather.
Again, you need someone who is competent installing the vents routes, fire proofing them penetrations and placing the extract and supply grilles to avoid short circuiting of routes within internal spaces.

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.
 
Thank you for your detailed reply ONG. I have just spoken to the engineer and have arranged a meeting with them to discuss everything. They will do a pre BER assessment of the build. I feel so relieved now.
Thanks again for all your help. I'm sure I'll be back looking for more advice over the coming months
 
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