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Insulation Thoughts - External v Internal

  • 27-02-2018 01:56PM
    #1
    sulli
    Registered Users, Registered Users 2 Posts: 163 ✭✭


    Hi,

    Just after buying a terraced house and starting to do it up bit by bit! We are starting with our sitting room (currently open plan) and doing the following to it

    - getting engineered wood floors fitted currently carpet over old floorboards
    - new skirting boards
    - plastering the walls then painting
    - blocking up a window ( used to be a door)
    - putting in double door
    - Internal insulation on the outside wall.

    and a few more small things, ballpark quote from one builder is 5-6k.

    My question is, we had another lad in who was telling us we should definitely get the outside wall externally insulated whereas the lad that quoted above said that we should be only looking at internally insulating it and that would be what most should recommend. For a terraced house, is there much point in externally insulating it and should just concentrate on internal? Thanks.


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Comments

  • #2
    Dardania
    Registered Users, Registered Users 2 Posts: 3,612 ✭✭✭Dardania


    external insulation is far more effective compared to internal. the price usually reflects that fact. 

    SEAI have some grants and guidance here: https://www.seai.ie/grants/home-grants/better-energy-homes/insulation-grants/

    In Ireland, external insulation is generally pretty well "regulated" e.g. the guys doing it are installing to SEAI standards, and are audited semi-frequently. It's a good result for standards.
    Whereas, internal insulation can be thrown up by anyone. It most likely will not be to a high enough standard, could leave "cold bridges" where condensation will form, and does nothing to assist with air tightness. So bear that in mind when receiving impartial advice from the chap quoting you for work.

    Suggest you consider ventilation measures and heating controls at the same time.


  • #3
    sulli
    Registered Users, Registered Users 2 Posts: 163 ✭✭sulli


    thanks for that! So would you not suggest insulate internally or would that tie us over for a while? When the fella was out and talking around the external insulation he said it would be best to wait until we are replacing the windows, hoping to do this next year?

    Also, when you say ventilation and heating controls?


  • #4
    bmm
    Registered Users, Registered Users 2 Posts: 912 ✭✭✭bmm


    Also, if the sizes of your rooms are already tight, internal insulation will make them feel tighter still. Light thru smaller windows is also impeded , but that probably is true of external also. Another advantage of external is you don't have to leave the builders in your house and all that comes with that ( hobnail boots etc.)


  • #5
    raxy
    Registered Users, Registered Users 2 Posts: 893 ✭✭✭raxy


    I moved into an end of terraced house & have been getting all the walls skimmed inside. I wondered about insulation but we didn't have the money so left it. Our heating for the first year came to €500. Spent a bit more this year but also used it more.
    I never prices getting the insulation done but doubt there would be enough of a saving in heating to justify the cost. Think my BER is D.
    I would leave the insulation for now & wait to get your windows done. Keep an eye on the heating costs next winter to decide if it's worth the expense.


  • #6
    Dardania
    Registered Users, Registered Users 2 Posts: 3,612 ✭✭✭Dardania


    In my own shoes, I wouldn't waste the money on internal insulation, unless I knew it was to a high standard (e.g. SEAI standard). If you are considering external at some point in the future, just hold on until then.

    With ventilation, it's just to make sure the house is adequately ventilated. I'm guessing this is an older house? Ventilation knowledge and standards have advanced a lot in the last 20 years, not to mention houses from earlier. It's a good idea to check it out now when semi-major work is being done, to prevent having to come back and do it later. It's also a condition for external ventilation grant aided by SEAI that the ventilation is adaquete. See:
    https://www.seai.ie/resources/publications/Homeowners-Guide-To-Ventilation.pdf

    With heating controls...often times older houses  (older than 10 years) didn't really have good control of the radiators. It was just switch on the boiler and blast the place with heat, and if you're lucky there's a thermostat to try stop overheating one of the rooms at least. Quite crude.
    Whereas if you were to look at fitting some heating controls (like TRV valves on each radiator and a heating programmer to split space heating and hot water control) you can get a high level of control. I worked out the numbers before, and in terms of energy consumption savings, proper heating controls were close enough to the savings achieved by externally insulating a particular house.
    So if you're going to put off doing insulation, maybe decent heating controls in the mean time can get you through a few years in relative comfort. SEAI also do a grant for it: https://www.seai.ie/grants/home-grants/better-energy-homes/heating-upgrade-grants/ and have a guidance document to explain more about it: https://www.seai.ie/resources/publications/Homeowners-Guide-To-Heating-Controls_Dec2017.pdf


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  • #7
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,146 Mod ✭✭✭✭BryanF


    Op can you just confirm your living rm floor is concrete? (If it’s suspended, you should down tools now, and have a rethink)
    Assuming concrete floors I would go EWI, but don’t do it until you can afford to the windows at the same time.


  • #8
    kev1234
    Registered Users, Registered Users 2 Posts: 112 ✭✭kev1234


    BryanF wrote: »
    Op can you just confirm your living rm floor is concrete? (If it’s suspended, you should down tools now, and have a rethink)
    Assuming concrete floors I would go EWI, but don’t do it until you can afford to the windows at the same time.

    What's the impact if the floor is suspended timber? Will EWI not be effective?


  • #9
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,146 Mod ✭✭✭✭BryanF


    kev1234 wrote: »
    What's the impact if the floor is suspended timber? Will EWI not be effective?

    You need to vent underneath a suspended floor from the external. This means you need to insulate and make the floor/joist zone air-tight, while still allowing ventilation to the subfloor. Therefore when you externally insulate you have the entire external perimeter base of the wall & all internal room adjoining base of walls cold from the ventilation.

    really external walll insulation means filling in the subfloor. Best do this now before spending money on flooring.


  • #10
    kev1234
    Registered Users, Registered Users 2 Posts: 112 ✭✭kev1234


    BryanF wrote: »
    You need to vent underneath a suspended floor from the external. This means you need to insulate and make the floor/joist zone air-tight, while still allowing ventilation to the subfloor. Therefore when you externally insulate you have the entire external perimeter base of the wall & all internal room adjoining base of walls cold from the ventilation.

    really external walll insulation means filling in the subfloor. Best do this now before spending money on flooring.

    Thanks for the reply, that makes perfect sense. Strange that the insulation companies I spoke to didn't mention this. Probably not in their interest to talk me out of EWI.

    I think we will be going with internal insulation in the existing part of the house anyway as I don't think we can replace the suspended floor with a subfloor.


  • #11
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,146 Mod ✭✭✭✭BryanF


    internal drylining: lack of insulation continuit - zone between first floor & ceiling and where internal walls meet the external for example.


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  • #12
    kev1234
    Registered Users, Registered Users 2 Posts: 112 ✭✭kev1234


    BryanF wrote: »
    internal drylining: lack of insulation continuit - zone between first floor & ceiling and where internal walls meet the external for example.

    Yeah I know it's not as good and I would prefer the EWI but unfortunately some decisions need to be evaluated to see if it's within the budget and will get the return needed. If I had the budget I'd probably backfill the existing suspended floor and install UFH and EWI. I don't think we can justify this though. The internal drylining with new windows and doors will at least improve on what we have albeit not as significantly.


  • #13
    sulli
    Registered Users, Registered Users 2 Posts: 163 ✭✭sulli


    BryanF wrote: »
    Op can you just confirm your living rm floor is concrete? (If it’s suspended, you should down tools now, and have a rethink)
    Assuming concrete floors I would go EWI, but don’t do it until you can afford to the windows at the same time.

    Its old floorboards, have been told that if i was to rip them up, insulate etc the cost would be significant...so best bet was to put new floor on top....in my laymans terms!!!! There is a vent outside that seems to run underneath the floorboard already if that makes any sense.


  • #14
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,146 Mod ✭✭✭✭BryanF


    sulli wrote: »
    Its old floorboards, have been told that if i was to rip them up, insulate etc the cost would be significant...so best bet was to put new floor on top....in my laymans terms!!!!

    Don’t waste your money laying a new floor

    Live in the house for a few months, ideally during the winter, you’ll quickly see why insulation and air-tightness of the floor is essential. I say this from experience.


  • #15
    Calahonda52
    Registered Users, Registered Users 2 Posts: 13,341 ✭✭✭✭Calahonda52


    BryanF wrote: »
    Don’t waste your money laying a new floor

    Live in the house for a few months, ideally during the winter, you’ll quickly see why insulation and air-tightness of the floor is essential. I say this from experience.

    +1
    https://www.nsai.ie/S-R-54-2014-Code-of-Practice.aspx

    “I can’t pay my staff or mortgage with instagram likes”.



  • #16
    kev1234
    Registered Users, Registered Users 2 Posts: 112 ✭✭kev1234


    BryanF wrote: »
    Don’t waste your money laying a new floor

    Live in the house for a few months, ideally during the winter, you’ll quickly see why insulation and air-tightness of the floor is essential. I say this from experience.

    Is there anything that can be done to improve the air tightness of the suspended floor without replacing it with a concrete floor? Taking up the boards and insulating beneath them perhaps?


  • #17
    Calahonda52
    Registered Users, Registered Users 2 Posts: 13,341 ✭✭✭✭Calahonda52


    kev1234 wrote: »
    Is there anything that can be done to improve the air tightness of the suspended floor without replacing it with a concrete floor? Taking up the boards and insulating beneath them perhaps?
    open the link I sent, its 280 pages on refurb, 12Mb

    “I can’t pay my staff or mortgage with instagram likes”.



  • #18
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,146 Mod ✭✭✭✭BryanF


    kev1234 wrote: »
    Is there anything that can be done to improve the air tightness of the suspended floor without replacing it with a concrete floor? Taking up the boards and insulating beneath them perhaps?

    Yes

    just use the search function this has been covered plenty of times


  • #19
    sulli
    Registered Users, Registered Users 2 Posts: 163 ✭✭sulli


    ok, so lots to think about...and there was me thinking we could get this sorted easily!!!! All we want is a decent sitting room!!!!:D:D:D:D:D:D:D:D:D Thanks for the advice lads, very helpful as per usual!


  • #20
    Dont Be at It
    Registered Users, Registered Users 2 Posts: 527 ✭✭✭Dont Be at It


    BryanF wrote: »
    You need to vent underneath a suspended floor from the external. This means you need to insulate and make the floor/joist zone air-tight, while still allowing ventilation to the subfloor. Therefore when you externally insulate you have the entire external perimeter base of the wall & all internal room adjoining base of walls cold from the ventilation.

    really external walll insulation means filling in the subfloor. Best do this now before spending money on flooring.

    In a similar situation as OP so I've being following this thread with interest.
    Just to confirm, does this reasoning regarding EWI apply to all suspended wooden floors or just ones that aren't insulated?
    Figure G.5 on page 244 of the NSAI document suggests EWI can be applied to insulated suspended timber floors without significant thermal bridging?


  • #21
    Dont Be at It
    Registered Users, Registered Users 2 Posts: 527 ✭✭✭Dont Be at It


    OP, just a heads up - some of the issues you're raising have been covered by the lads in these two threads I started recently. Might be of some use!
    https://www.boards.ie/vbulletin/showthread.php?t=2057836559
    https://www.boards.ie/vbulletin/showthread.php?t=2057829143


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  • #22
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,146 Mod ✭✭✭✭BryanF


    Dont Be at It wrote: »
    In a similar situation as OP so I've being following this thread with interest.
    Just to confirm, does this reasoning regarding EWI apply to all suspended wooden floors or just ones that aren't insulated?
    Figure G.5 on page 244 of the NSAI document suggests EWI can be applied to insulated suspended timber floors without significant thermal bridging?

    Wouldn’t be the only flaw in that document

    The 2d thermal calc doesn’t seem to allow for ventilation of the subfloor. When I insulated my suspended floor I attempted to insulate the rising wall to mitigate this thermal bridge - not convinced it was affective


  • #23
    Dont Be at It
    Registered Users, Registered Users 2 Posts: 527 ✭✭✭Dont Be at It


    BryanF wrote: »
    Wouldn’t be the only flaw in that document

    The 2d thermal calc doesn’t seem to allow for ventilation of the subfloor. When I insulated my suspended floor I attempted to insulate the rising wall to mitigate this thermal bridge - not convinced it was affective

    Interesting. Did you insulate the rising wall internally or externally?

    So broadly speaking, IWI provides better insulation than EWI where there is suspended timber floor?

    Earlier in the thread, you mentioned replacing the windows and installing the EWI at the same time... is installing EWI and leaving the old windows insitu a complete no no?


  • #24
    Lumen
    Registered Users, Registered Users 2 Posts: 31,276 ✭✭✭✭Lumen


    BryanF wrote: »
    You need to vent underneath a suspended floor from the external. This means you need to insulate and make the floor/joist zone air-tight, while still allowing ventilation to the subfloor. Therefore when you externally insulate you have the entire external perimeter base of the wall & all internal room adjoining base of walls cold from the ventilation.

    really external walll insulation means filling in the subfloor. Best do this now before spending money on flooring.

    I don't understand why the joists need to be ventilated if the external insulation goes down to foundations and the floor is kept leaky. Surely the joists are then inside the heated, ventilated envelope of the building, like those between floors? There won't be any temperature gradient to trigger condensation.


  • #25
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,146 Mod ✭✭✭✭BryanF


    Dont Be at It wrote: »
    1. Interesting. Did you insulate the rising wall internally or externally?

    2. So broadly speaking, IWI provides better insulation than EWI where there is suspended timber floor?

    3. Earlier in the thread, you mentioned replacing the windows and installing the EWI at the same time... is installing EWI and leaving the old windows insitu a complete no no?

    1. Internally. When I finish extension, I change windows & ewi next .
    2. No, definitely not. I just did this because I had the floor up.
    3. Just a waste, as all linear junctions between ewi & windows will attention when you get around to changing the windows, return visit of ewi contractor would be painful.


  • #26
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,146 Mod ✭✭✭✭BryanF


    Lumen wrote: »
    I don't understand why the joists need to be ventilated if the external insulation goes down to foundations and the floor is kept leaky. Surely the joists are then inside the heated, ventilated envelope of the building, like those between floors? There won't be any temperature gradient to trigger condensation.
    Under floor should be vented.

    Will you be providing some kind of continuous dpc/radon/ moisture barrier ( in an existing situation) around ( and through) every rising wall and across the ground under the floor joists?

    You don’t want the dank, rotting situation where vents have been blocked when ewi was installed.


  • #27
    Dont Be at It
    Registered Users, Registered Users 2 Posts: 527 ✭✭✭Dont Be at It


    BryanF wrote: »
    2. No, definitely not. I just did this because I had the floor up.

    Okay - but were you not saying that EWI means filling in the sub floor in Post 9?
    Or did you just mean that this is the optimal solution (when budget allows) when installing EWI but that even with insulated suspended timber floors, EWI is still preferable to IWI?


  • #28
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,146 Mod ✭✭✭✭BryanF


    Dont Be at It wrote: »
    Okay - but were you not saying that EWI means filling in the sub floor in Post 9?
    Or did you just mean that this is the optimal solution (when budget allows) when installing EWI but that even with insulated suspended timber floors, EWI is still preferable to IWI?

    Ewi is preferable to Drylining


  • #29
    kev1234
    Registered Users, Registered Users 2 Posts: 112 ✭✭kev1234


    Calahonda52 wrote: »
    open the link I sent, its 280 pages on refurb, 12Mb

    I've been checking the NSAI document you referred to and TGD Part L along with a number of the many similar threads mentioned on here and by all accounts the EWI seems to be the preferred option from those who are frequent contributors, albeit some people are confident that IWI is perfectly fine and not as bad as an alternative as sometimes suggested. It seems in all of the threads there are arguments for and against both?

    The documents suggest that in putting internal insulation on hollow block wall you need to ensure proper installation to guard against condensation and thermal bridging but they don't rule it out as a viable option. Surely this wouldn't be covered in Construction Regs and under SEAI grants if the effects were essentially guaranteed and as bad as some suggest?


  • #30
    Dardania
    Registered Users, Registered Users 2 Posts: 3,612 ✭✭✭Dardania


    As I said in original post - IWI is fine if installed correctly. That’s a high standard to aim for. And far from every general builder has the skills to install it 100% correctly.


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  • #31
    kev1234
    Registered Users, Registered Users 2 Posts: 112 ✭✭kev1234


    I am still looking at the possibility of EWI but I am unsure as to if it can be done in my situation given that I will be building as close as possible to the neighbours existing side extension. Presumably for EWI to be installed there needs to be a space that the installers can get into to install it onto the wall? I will be looking to build our side extension wall as close as possible to the neighbours existing wall. Could EWI be installed here? Seems impossible to me.

    This installation difficulty along with my existing suspended timber floor has been moving me towards going with IWI on the existing external hollow block walls and building a cavity wall with partial fill on the new extension walls (coloured yellow in attached image).

    https://imageshack.com/a/img922/8948/zSxxvy.jpg


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