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Existing House and thinking of retrofitting A2W

  • 19-11-2019 11:55am
    Registered Users Posts: 24 gg3390

    Hello all,
    I'm looking for some advice re: my options for renewable energy in a 2004-built house.
    The house was a self-build in 2005, however I was not as clued in during the build as I should be in relation to insulation and the like, but nontheless the house is insulated to a relatively ok standard. 2-storey 2900 sq. ft., hollowcore, and converted attic. Pumped bead insulation in the cavity done in 2011. Attic converted and crawlspaces well insulated with rockwool throughout.

    We have no underfloor and rads with oil burner throughout the house. One chimney, with fitted stove.

    The problem is the house is never quite warm, even though we burn probably approx €1500 oil throughout the year. Were we to warm the house to a very comfortable level my guess is that our oil consumption would shoot up dramatically. Back when the house was built there were so many horror stories regarding underfloor heating/geothermal etc., that I (wrongly) erred on the side of caution and went with tried and tested oil. This was probably my worst decision, as retrofitting underfloor now is not really an option.

    So, i'm now in the process of trying to examine all the ways of improving air-tightness of the house, and improving it's warmth. While this might not be agreed with by readers, my idea of comfort is having a constant maybe 20/20degree heat throughout the house, and would be willing to pay for same. Considering our oil and electricity bills right now, the combined total is probably in the region of 3-4k per year, and the house is only periodically warm (during the cold months). I'd be well happy if, after some work or retrofit I was still baying the same amount of money, but had heat 24/7. Others here show savings of x €€€ after a2w, geothermal etc., with sub €1000 bills, and this is great, but for me, the above would be a result.

    Our house uses lots of gadgets, servers running, submersible pumps for well water, air-pumped septic tank etc., so baseline electricity demand is quite high. I'm in the process of trying to lower this current baseline at present, and have replaced 50 downlighters with 5w LED types as a start. Also moving a lot of the computer gear to low power in addition.

    I think one of my greatest issues is possibly the air-tightness of the house, and back in 2004, either I did not know, or the concept of air-tightness was not talked about much. Thus, I think that the hollowcore was not sealed at the wall level, and even today I can feel small draughts at under the recessed lights throughout the ground floor.

    So, after the long intro, looking for any advice on the following :-

    1. Retro sealing the joints in the hollowcore - madness??? I was thinking of potentially drilling the plasterboard close to the wayy and pumping in spray foam or the like in an attempt to seal the joint.

    2. I'm replacing hinges on windows which are worn, which results in some windows not having the required tight close and seal to the frame. Also addressing sealing of front/back doors.

    3. There is no insulation on the rafters in the crawlspace, just the floor and upright part to the back of the conversion. The top ceiling of the attic is insulated though. The rafters were left without insulation as was told the roof needs to breathe. The current insulation goes very close to the wall plate, but not over it. The crawlspace is very cold in comparison to the attic, so the insulation should be doing its job here, but I'd guess it is still very leaky in terms of airflow due to the vents in the soffit.

    I would love to change to an A2W heat pump, and replace the regular rads with aluminium, and if my energy bills remained the same (for a 24/7) comfortable temp I would be very happy, but I feel this in itself would not work.

    I'm open to any suggestions whatsoever, especially on remedial action I could possibly take on the existing house. I wish I had done more research 16 years ago!

    Thanks in advance.


  • Registered Users Posts: 2,544 ✭✭✭ MicktheMan

    1. Waste of time.
    2. Good
    3. Crawl space is outside your thermal envelope so should be cold and well ventilated. This ventilation should not however interfere (leak) with the space inside your thermal envelope.

    You mentioned a lot of down lighters, are they recessed into your ceiling?

    Have you had the house tested for air tightness? If not, why not?

  • Registered Users Posts: 24 gg3390

    Thanks for the reply.

    Yes - as the crawlspace is cold in comparison to the house it does appear that the insulation is doing its job, and I expected it to be much colder.

    Where I have access, i.e. upstairs, I have sealed all recessed lights with those flame retardent pots and taped the joint. There is however a hole in the top of the pot - probably originally to allow the heat from the non-LED bulbs escape. I'm unsure at this point if, after using LED bulbs (240v) if I can also seal this hole and cover fully with insulation.

    Downstairs I have no access to the recessed light except whatever access I can get from the ceiling - due to the hollowcore.

    No - I have not yet done an airtightness test - am awaiting somebody to get back to me about doing so, and also getting an IR camera to see of there is any glaring leaks.

    Thank you

  • Registered Users Posts: 24 gg3390


    As a further question in relation to your comment about leakage of ventilation to the inside of my thermal envelope - this is what I'm trying to address, and the draughts from the recessed lights downstairs are those that concern me. I don't know where the draught might be coming from, and indeed an air-tightness test might shed some light on that. However, considering the hollowcore is sitting on the inside leaf, and the cavity has both insulating board, and has been pumped, I cannot figure out where exactly this might be from.
    Certainly, making good the windows and doors might help in this regard.

  • Registered Users Posts: 2,544 ✭✭✭ MicktheMan

    The cavity (whether pumped or not) in a cavity wall is considered outside from an airtightness pov. And as the concrete slab was not wrapped for airtightness during construction then there is no barrier present.
    Your airtightness test should leave you in no doubt about what is happening and more importantly what you can do about it.

  • Registered Users Posts: 24 gg3390

    thank you for the information.

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