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Airtightness for new house

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Comments

  • Registered Users Posts: 153 ✭✭ liamolaighin


    Have actually been considering the solid fuel stove alright since. Think it'd be nice n cozy n improves the BER no end. So if I do go this route would people generally agree that the membranes are a good idea as long as I have enough natural ventilation. Thats the gist i'm gettin so far


  • Closed Accounts Posts: 5,433 ✭✭✭ sinnerboy


    Guess what I voted ?


  • Registered Users Posts: 335 ✭✭ Naux


    Assuming that you put in the airtight membrane and achieve a high level of airtightness in your house, does this mean that you must then install a HRV unit to ventilate the house?


  • Closed Accounts Posts: 5,433 ✭✭✭ sinnerboy


    Yes . If you achieve Q50 / 7 or better then you will need HRV


  • Registered Users Posts: 153 ✭✭ liamolaighin


    So should I be looking at more insulation, using tapes and membranes etc instead of going down the geothermal route. I know the answer is yes I should make it as cheap as possible to heat the house but would it make sence going with geothermal in a house with low heating requirement. I dont want to go with ICF so is there any danger a standard block build with lots of insulation and airtightness will be too airtight. Dont want to spend a fortune either just for the sake of a rating.........


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  • Registered Users Posts: 335 ✭✭ Naux


    sinnerboy wrote: »
    Yes . If you achieve Q50 / 7 or better then you will need HRV

    What would be a rough cost estimate per sqft for the airtightness detail?Is it the 12 euro per sqft as previously mentioned?

    From what I've seen in previous posts 5-6k would be the average cost of a HRV system. Open to correction of course!

    I'm just trying to get an idea of the total cost or making a house airtight. I know you will definitely save on energy costs with it but I'm just wondering about the capital costs/outlay to achieve it.


  • Closed Accounts Posts: 5,433 ✭✭✭ sinnerboy


    Those are ok budget costs . It is difficult to know what to do - if you don't do a DEAP assessment .

    With a DEAP assessment to "play" with you can look at alternative methods of complying with b regs and do cost/benefit exercises then .

    Your shooting in the dark otherwise


  • Closed Accounts Posts: 112 ✭✭ Lightning McQue


    Folks

    I did a deap assessment which indicated that I would be making the house airtight and putting in a MVHR system but the MVHR had a negative impact on the BER whereas the triple glazing had a positive impact on the BER.

    It seems that holes in the walls (natural ventilation) were better from a BER perspective than a controlled ventilation system. It seems strange.

    Anybody else had this type of experience?

    lightning


  • Subscribers Posts: 36,016 ✭✭✭✭ sydthebeat


    I did a deap assessment which indicated that I would be making the house airtight and putting in a MVHR system but the MVHR had a negative impact on the BER whereas the triple glazing had a positive impact on the BER.

    a few points.

    1. DO NOT use the default HRV values,, they are terrible. Search the SAP Aeppndix Q for figures, choose a decent efficiency and fan power.

    2. HRV systems show energy conservation at good levels of air tightness. 0.5 air changes per hour is not good.... aim for at least 0.3

    3. building shape has a significant effect on HRV systems. Large single storey buildings with angular forms will fair worst. Compact two storey etc fair best.


  • Registered Users Posts: 1,137 ✭✭✭ holdfast


    Hi lighting go to the sei website and download the correct procedure for dealing with HRV. Use the default if you cant find the unit on the sap index. You have been using the default unit setting which are very poor when comapred to units on sap index.


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  • Registered Users Posts: 43 ✭✭✭ Ferocious


    Syd, just picking up point 3 there.
    I'm building a single storey house. Like some of the previous posters, I've been deliberating about airtighness membranes & HRV systems. I intend to tape up windows, doors and wall/ceiling junctions, just not sure if this is enough.

    How much less efficient is HRV in a single storey?
    I haven't done the DEAP calculation yet, will this make it clear if there is much to be gained by using mhrv?
    At what stage of construction should the first air-blower test be done?


  • Registered Users Posts: 1,137 ✭✭✭ holdfast


    The first test should be done after windows are in and the house is sealed. Yes it will make it clear to you to put in air tightness test results and hrv unit details into deap to show how much energy could save. the loss in % eff will depend on how complex the deign is more turns in pipes more the loss which is the same for complex strucutres to lose more energy due to greater surface area.


  • Closed Accounts Posts: 112 ✭✭ Lightning McQue


    Folks

    I used the SAP appendix, 90% efficiency and 0.3 air changes. The house is a two storey with an angular shape. I presume this explains it or is it the electricity the fan will use?

    Lightning


  • Subscribers Posts: 36,016 ✭✭✭✭ sydthebeat


    Folks

    I used the SAP appendix, 90% efficiency and 0.3 air changes. The house is a two storey with an angular shape. I presume this explains it or is it the electricity the fan will use?

    Lightning

    whats the specific fan power?

    have you any chimneys or open flues?? any intermittant fans included?

    what sq ft?


  • Closed Accounts Posts: 112 ✭✭ Lightning McQue


    Syd

    I cant remember the specific fan power.

    I just remember the assessor inputting the xpelair unit and it had a 70% efficiency which is poor and he then increased this to 90% to see what effect this would have. So I will look for another company. The assessor said that the HRV was costing me money and that I shouldnt put it in, that I would be better to go with natural ventilation. Confused at this stage or is the software flawed.

    I will be installing two fireplace inserts.

    The area of the house is 314m2 and if I convert the attic it will add another 40m2. I am making provision for this.

    Lightning


  • Closed Accounts Posts: 2,948 gizmo555


    The assessor said that the HRV was costing me money and that I shouldnt put it in, that I would be better to go with natural ventilation. Confused at this stage or is the software flawed.

    Very interesting and detailed discussion on Mark Brinkley's blog "House 2.0" here:

    http://markbrinkley.blogspot.com/2009/11/whither-mvhr.html

    I suppose the key point to bear in mind when considering your assessor's comment is that HRV is not just about saving energy and reducing costs.


  • Registered Users Posts: 154 ✭✭ morning delight


    On the question of airtightness, I've chatted with the architect and an energy consultant and the feeling is 1.5m3/hr is what we can hope for with best practice blockwork cavity wall construction.

    My question is, Is trying to get this down to 1m3/hr worth it?


  • Registered Users Posts: 2,576 ✭✭✭ mr_edge_to_you


    Well it's all in now anyway. Seeing it in makes easier to see how it will be valuable in the long term. Thanks again guys.


  • Registered Users Posts: 996 ✭✭✭ Technophobe


    Hi Mr Edge to you...

    Can you maybe describe in a little detail what exactly they did for you and using what..??

    This may help all interested here to understand more clearly what the concept involves (in your case anyway)and what you/they get for their money to a degree (you have previously stated your costs per your builder in an earlier post)...

    thanks


  • Registered Users Posts: 2,576 ✭✭✭ mr_edge_to_you


    Hi Mr Edge to you...

    Can you maybe describe in a little detail what exactly they did for you and using what..??

    This may help all interested here to understand more clearly what the concept involves (in your case anyway)and what you/they get for their money to a degree (you have previously stated your costs per your builder in an earlier post)...

    thanks

    In my plain language here goes:

    First off all, all window and doors were taped around with "Airstop" tape. It's about 1.5inches wide and looks like cheap paper tape but it is actually quite strong.

    There is also a few rolls of a heavy duty plastic membrane running under the ceiling (1st floor/attic) joists and down about 2 metres on the wall plate. All the these various sheets are overlapping and sealed over with the aforementioned "Airstop" tape. The plasterboard is then put on over the membrane. He has only used the membrane between the frist floor ceiling and our attic.

    Looking at the work involved it is all labour! Builder said as much himself. He has said he has kept the cost to a minimum so it should be a few hundred quid less than €1500. You could probably do it all over the house from top to bottom (applying the membrane sheeting) but it would cost an awful lot by the looks of it -I'm open to correction on that though.

    That's about as much as I know about it. Sorry.


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  • Registered Users Posts: 996 ✭✭✭ Technophobe


    Thanks Mr Edge...

    That's detailed enough for me....:)
    More importantly, it may allow people here make decisions based on now knowing (in your case anyway) what is actually done and what you get for your money...

    thanks again


  • Closed Accounts Posts: 2 billyboburban


    I've heard of a couple of people who installed triple glazing (not sure what else they may have had done because I heard this 3rd hand) but all the wood in the house warped because of the dry air in the house. One couple went on holidays for a week and came home to find the dining table had split in two.

    Has anyone else heard of this happening? Could triple glazing alone be responsible for this? :confused:


  • Subscribers Posts: 36,016 ✭✭✭✭ sydthebeat


    I've heard of a couple of people who installed triple glazing (not sure what else they may have had done because I heard this 3rd hand) but all the wood in the house warped because of the dry air in the house. One couple went on holidays for a week and came home to find the dining table had split in two.

    Has anyone else heard of this happening? Could triple glazing alone be responsible for this? :confused:

    Timbers warping is due to inadequate ventilation, not anything to do with windows.

    Sounds like a newly built house that hadnt been allowed to dry out properly yet, and they went off without thinking about allowing constant ventilation to aid the drying out process while still having the heat turned up high.


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