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  1. #1
    Join Date
    Jun 2011
    Posts
    3

    Default Triple glaze roof windows/skylights

    Hi all,
    Building a passive house in Galway, starts in a couple of weeks. I need advice on roof windows. Have three to put in. Velux and Fakro and coming in at similar price. I cant seem to get a quote for non-openable roof windows for velux or fakro. I was advised these would let out less heat than openable windows. The skylights they have are for flat or low pitched roofs and ours is 40 degree pitch.
    Any advice would be appreciated as budget is low and would like to get non-openable ones as they are going in double height (unreachable) spaces.
    Thanks
    Haggini

  2. #2
    Join Date
    Jul 2010
    Posts
    207

    Default

    Haggini, Hi - couple of pointers, for the most part Northern European countries specify triple glazing but it's not cheap and Ireland is not per se a 'cold' country.

    Low emissivity coating(s) applied to a window can increase the insulation factor as also argon gas (optimal spacing 1/2") separated by the pane(s) or better still the more expensive krypton gas having an optimal spacing of 3/8".

    I don't know if you done the math or not but the pay off difference in a mild climate such as yours between double and triple glazing is negligible in terms of the energy expended and, all the more so if you add in low-e (emissivity coatings)

    As spacings vary with type of gas so the window weight(s) need to be factored into the calculations with potential adverse impact on surrounding structural framework costs.

    In summary, given Ireland's moderate climate triple glazing is very possibly not going to give you an ROI and it's probably best reserved for schools and hospitals where, it serves well as a noise pollution abatement solution derived from triple glazing's acoustical properties.

    Hope it helps

    pete
    Last edited by etep; 25th January 2012 at 06:18 AM.

  3. #3
    Join Date
    Aug 2007
    Location
    Dublin
    Posts
    196

    Default

    Quote Originally Posted by haggini View Post
    Hi all,
    Building a passive house in Galway, starts in a couple of weeks. I need advice on roof windows. Have three to put in. Velux and Fakro and coming in at similar price. I cant seem to get a quote for non-openable roof windows for velux or fakro. I was advised these would let out less heat than openable windows. The skylights they have are for flat or low pitched roofs and ours is 40 degree pitch.
    Any advice would be appreciated as budget is low and would like to get non-openable ones as they are going in double height (unreachable) spaces.
    Thanks
    Haggini
    You would be looking ideally to get class 4 airtighness and treble glazed (3G) with an insulated flashing, your skylights are exposed to the sky which can be routinely less than -60 degrees celcius, not worth scrimping here of all pkaces. Odly enough fixed rooflights perform worse in our airtigness tests than operable pivot ones. Fakro has an FTT thermo U5 window at airtightness class 2 but the new U6 and U8 window are at airtighness class 3. Velux have a new 3G window The Variant --65 with packages is apparently an airtighness class 4. Difficult to get this info from tradecraft and velux. These windows are not carried as stock items and have to be ordered form the continent.

    http://www.ribaproductselector.com/D...l/20120091.pdf

  4. #4
    Join Date
    Jun 2011
    Posts
    3

    Default

    Thanks for the advice, I got quotes for the U6 and U8 Fakro windows, they are very high performing but pricey! As the house has only a heat ventilation system to heat it though we will probably have to find the money somewhere. Ideally you wouldnt put any roof windows in a passive house but its great to have the light, esp in winter.

  5. #5
    Join Date
    Aug 2007
    Location
    Dublin
    Posts
    196

    Default

    Be careful designing the ventilation system to carry all your space heating as it can only supply about 2 to 2.5 Kw's @52 degrees. On a dark cold January week, with low occupancy, this might not be enough to keep with the house above comfort levels, even if it is heating continuously 24/7. So make sure to design with worst case weather data rather than mean average data. Air just isn;t as effective as water for delivering heat, so it may well be worthwhile to have a backup such as a stove or a couple of plug in rads.

  6. #6

    Default

    Quote Originally Posted by haggini View Post
    Hi all,
    Building a passive house in Galway, starts in a couple of weeks. I need advice on roof windows. Have three to put in. Velux and Fakro and coming in at similar price. I cant seem to get a quote for non-openable roof windows for velux or fakro. I was advised these would let out less heat than openable windows. The skylights they have are for flat or low pitched roofs and ours is 40 degree pitch.
    Any advice would be appreciated as budget is low and would like to get non-openable ones as they are going in double height (unreachable) spaces.
    Thanks
    Haggini
    We got two tripple glazed rooflight from keylite. U=1. They are much much cheaper than the above brands but you pay a premium for the tripple glaze. They will do a deal with you. I think they are based in the north but have reps down here. The builder was very impressed with them as they came with dark grey flashings when we wanted black to match rooftiles. They called straight out to the site and changed out the flashing without any nonsense. Like you we wanted ones that didn't open but they dont exist anymore. They look great.

  7. #7
    Join Date
    Jun 2011
    Posts
    3

    Default

    We went with the triple glaze facro in the end. They are in now are we are happy with them. Yes we will be putting in a stove for those cold january evenings! Although we have talked to lots of people who have our house already (not sure if I can say the name of the company here so I wont) and if they have a stove they say they dont use it very much. Thanks for all your replies

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