Retrofit + extension + energy upgrade

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jashar99

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We have nearly completed on buying a house in west of ireland. 1970's Detached 2 storey house with attached garage with is seperating from the house and will have to be knocked. Thereis also an unauthorised extension to the rear, built about 10yrs ago, with a very low pitched gable roof (retention going through, decesion in 3 weeks) giving a kitchen extension and sun room/family room.

We plan to knock the garage and rebuild to give a 2 storey extension with bedroom upstairs. Also i forsee many problems with condensation and we will probably have to change the roof on the extension if it all goes through, perhaps to a lean -to roof and put in velux windows.

the finish is pebble dash, block construction with cavity.

I would really appreciate any advice people have with regard to energy upgrade at the same time as extension. I was thinking of externally insulating and replacing doors and windows with more energy efficent ones, also allowing windows to be moved out. I also was planning on puting in a heat recovery system. There will be zoned heating controls, and the open fire with be replaced with an insert stove.

I wonder is it worth, given all this work to conisder replumbing and rewiring and at the same time insulating the ground floors?

Thinking of the future, is it worth considering an air to water heat pump at the same time. There is oil fired central heating system

upstairs in bedrooms, there is pine floors, is it worth lifting and insulating these?

Thanks for any comments.
 
you've a list of work there:D

MVHR and/or heat pumps require a super insulated, air-tight building envelope to be even remotely efficient. so in very simple terms your list is in the right order

  1. consider existing house as part of the extension process
  2. consider building fabric (insulation, windows and air-tightness first)
  3. consider ventilation strategy
  4. and lastly suitable heating source (after you've reduced the need for it)

  • the important things with the EWI will be the quality of the product and install + the overlap at foundation, eaves/attic and Win/Dr opes.
  • if the floor is concrete, i would be more inclined to bring the EWi down to foundation externally and not bother trying to insulate the floor
  • if the existing Elec and plumbing are deemed ok. leave well enough alone - you'll probably end-up changing the guts of the heating pipes and electrics if nothing has been changed in 40 years:(
  • as regards MVHR - you could allow for its ducting and install, but hold off on the final decision until works are far enough advanced to carry out a air-tightness test. If the resulting air-leakage figures are high, perhaps a positive input or demand controlled system could be installed instead of a heat recovery system
  • get 1:5 details prepared of the major junctions (particularly win/dr and eaves) to show the builders the air-tightness & thermal continuity attention required
  • whoever does this should also be able to calc your expected kwh/m2/y to allow for a suitably sized and selected heating source
  • as regards the floors upstairs - whether they require insulation or not depends on the success of the EWI wall/attic overlap and (the very separate issue of) how air-tightness is achieved in this location
whoever is going to do your extension design should be able to (or willing to employ a third party) who is au fait with current building regs/low energy/ passive house detailing - please note that IMO this is not a BER assessor but more likely a passive house designer with architectural background)
 
Thank you lowCO2design for such a considered reply. could you recommend any information sources with regard to deciding what type of EWI to choose. Is it necessary to cavity fill as well as EWI? Hopefully the retention issue goes through and I will soon be engaging an architect with passive design background
 
EWI general information sources - no I'm afraid I not aware of any and Yes pump the cavity

we can presume that all will have NSAI certification. the tricky business is deciphering all the jargon and actually getting the contractors to install the stuff properly, thats why I tend to go through the system providers

weber is my preferred budget option (the rep will give you a local installer)

sto is my preferred system but you pay for it!

i like this stuff as its not an oil based product[broken link removed] but the two EWI system provider above offer a rigid mineral wool insulation which is at least recyclable at its end of life.

there are many more EWI systems and products available in Ireland and its up to your architect to be extremely proactive in selecting, reading the fine print and getting guarantees/quality assurances

this is a good article to start with on the general upgrading works that you may be facing
[broken link removed]
 
On another matter, make sure that you do the following if you have not already:

1. Commission a building inspection report to be carried out by a competent consultant, as dry/wet rot may be present and many reports fail to spot it.

2. Have someone check and double check the original planning permission for the property with regard to site boundaries, and the location of the septic tank (i.e. does whats on the ground match the planning permission, and does that match the land registry maps?).
Also be aware that it is possible that you may be required by the Planning Authority to upgrade the existing system as part of any existing or future planning permission (i.e. for your extension).

As regards the useful advice given by lowc02design, I would only question the viability of MVHR if you are not planning to make the house really, really airtight.


www.studioplustwo.com
 
thanks threebedsemi, i'm thinking alright we'll have to extend to get air tightness if we plan to put in MVHR to be effective
 
threebedsemi said:
As regards the useful advice given by lowc02design, I would only question the viability of MVHR if you are not planning to make the house really, really airtight.
Click to expand...
lowCO2design said:
MVHR and/or heat pumps require a super insulated, air-tight building envelope to be even remotely efficient. ....
as regards MVHR - you could allow for its ducting and install, but hold off on the final decision until works are far enough advanced to carry out a air-tightness test. If the resulting air-leakage figures are high, perhaps a positive input or demand controlled system could be installed instead of a heat recovery system
Click to expand...

jashar99 said:
thanks threebedsemi, i'm thinking alright we'll have to extend to get air tightness if we plan to put in MVHR to be effective
Click to expand...
this makes no sense? surely the existing house will not be separate from the new extension?
 
apologies, i meant to say we'll probably have to "externally insulate" rather than "extend" to achieve good airtightness. Re-reading my above comment makes NO SENSE
 
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