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Ventilation, Air tightness, and external insulation (also PM for usable contactable architects)

  • 22-09-2022 5:28pm
    Registered Users Posts: 22


    I'd welcome some advice. We're planning a deep retrofit on a late 1990's semi by the seaside in North Dublin.

    The house is cold, partly because the builder seems to have had a passion for vents. For example, there are three in the kitchen.

    We may get external insulation to the rear and side, with new windows, and cavity insulation to the front (can't alter the facade). We intend a heat pump, solar PV, and (eventually) batteries.

    I inquired about ventilation, and the advice is to use the vents, as they are. How does this work, and how well/badly does it affect energy? I'm not much interested going for ducted ventilation, both for cost, and for sanity reasons!

    On a side note I'd also welcome PM's about possible architects. Every one we've contacted so far is either out of the business, or does not reply.




  • Registered Users Posts: 72 ✭✭Punchin A Keyboard

    There are various ductless systems which operate by sucking air out for 60 to 90 seconds heating up some stratum as the air passes over it and then reverses the fans to suck in air from outside. As the inbound air passes over the stratum it gets heated up.

    I will probably be getting ducted upstairs and ductless downstairs in my semi deep retrofit, if it ever kicks off.

  • Registered Users Posts: 1,130 ✭✭✭DC999


    There's a few bits in this. So might be best to simplify it and say what's the key stuff you wanna find out.

    Insulate: I'd suggest change the order. Insulate first which is your primary Q here of course (but not something I can advise on how to do). And only when you have a high BER rating, then consider heatpump. Read the other forum on heatpumps. Heat Pumps - post here. - Page 65 — - Now Ye're Talkin'. Good info in that. I don't have one but do have a drafty, uninsualted house. And they should not live there. Will underheat and cost a fortune.

    Ventilation: Others might chime in, not one I know.

    Solar PV: Can be a separate part. There's a long lead time so you could start it now as won't impact the insulation work. You can get solar as a service from €40 per month if you need to use the cash elsewhere. That includes the grant already deducted at that price per month. Back of envelope stuff, you won't see much change from 10k for solar (depends on what you get of course) - but that's a ballpark. 5k would be a steal, so somewhere between 5-10k just for panels (no battery, no EV charger). Dive in here when ready: Interested in Solar PV? Read this FAQ first. — - Now Ye're Talkin'

    Batteries: payback is very questionable at moment with decent FIT on solar (15c+). So park that for now I'd suggest. Natural time to get a battery is as part of the solar install but think long and hard about it and see if maths works for you. Won't run a heatpump from it, they are way too power hunger. And if you've an EV or expect to have, that's the largest battery you'll get. In your case, it's better to spend the cash elsewhere on energy reduction as you've a large body of work in flight it seems.


  • Registered Users Posts: 22 astaines

    All very helpful, so thanks.

    We do plan to do the insulation first, and then the heatpump. Solar is more a personal project, than a investment, and given we have an EV we may well never get to home batteries! The ventilation is probably the big remaining uncertainty, but I'll ask specifically about the devices you suggest. Other comments welcome!

  • Registered Users Posts: 1,892 ✭✭✭SD_DRACULA

    My house, built around '97 had and has no big vents in the walls but the windows have vents in the frame which I suppose is another way of doing it.

    Look into that since I'm sure you have to replace doors/windows too.

  • Registered Users Posts: 72 ✭✭Punchin A Keyboard

    Pv can go in any time make sure you don't get overcharged.

    Of course insulate and airtight where possible but if you do you also need to ventilate to prevent the house from becoming a health hazard.

    At least the one thing the seai are doing is making sure that a house is fit for a heat pump before giving a grant. One thing to note is the sizing of your current rad pipes as they may need to be replaced for bigger ones if a hp goes in.

    There are more grants available with a one stop shop for doors and windows but overall the process is not good.

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  • Registered Users Posts: 9 Kev3434

    Hi. I wish you the best of luck with the works. You really need to put serious thought into airtighness. It is difficult with a retrofit however. For a heat pump to work efficiently, it needs both a well insulated home and airtightness (with controlled ventilation). Any draughts, no matter the level of insulation, will result in your heat pump working harder, costing you money in the long run.

    Your house can be sized for the amount of ventilation required (either mechanical or the background vents you currently have). If it was my house, I wouldn't look to fit a heat pump and leave the background ventilation as you currently have. You can PM me for more detail on this if you wish.

    As stated above, I'd pass on the battery. I have a 3kw PV system which provides us with more than we need and the feed in tariff announced earlier in the year is a welcome bonus. After the grant it cost me €2,700, 2 years ago. Small company and great to deal with. Happy to pass on details if you wish.

  • Registered Users Posts: 2,147 ✭✭✭cubix

    If going to all the hassle of a deep retro fit and making the house airtight I would suggest putting in ducting for mechanical ventilation (heated/ non heated) even if not doing now as the ducts will be minimal cost but a serious pain to retro fit once cielings/ wall slab goes up.

  • Registered Users Posts: 291 ✭✭spose

    If putting in that investment to make the house more efficient and comfortable why would you leave a big hole in the wall to undo all the benefit. I put in the hrv as a retrofit as part of other work and would never go without now. If I was building again it would be one of the first things on my list of must haves.