passivhaus windows

We have velfac,  speak to the manufacturer, velfac trained our fitters to install them 

Internorm here(we got them discounted as I'm an architectural designer), multi open style, they open inwards which take some getting used to but in reality is fine as we usually just crack open the top half (summer purging at night) so you can still have things on the window sill. We had a quote for velfac at the time which were a fair amount cheaper and are also nice but internorm probably slightly better quality frame/controls. If building again I'd prob save a few quid and go velfac as you rarely open windows on a passivhaus. Velfac open outwards and are still very nice windows. Also look at green building store, very good quality.

Thanks. I'll take a look at those.

There should be a list of approved installers on the window company's website.

They are quite easy to install either by lug fix or through fix .

I have three velfac windows in my shed.

Thanks - I’m not familiar with all the manufacturers so looking for suggestions of them.

installers would also be good as a poorly installed window has very poor thermal efficiency.

Are you building a passivhaus with mvhr and high levels of airtightness overall, or just want high performance windows?

installers would also be good as a poorly installed window has very poor thermal efficiency.

What is the rest of the house?

If building again I’d prob save a few quid and go velfac as you rarely open windows on a passivhaus.

@nt80085

really?  in hot weather definitely want windows open in the evenings to bring in cool air quickly.  MVHR doesn't give a quick enough air change.

We've got inward opening and not sure I'd do it again - I think they're best coupled with external shutters rather than curtains or blinds.  The advantage is you can generally leave them tilted if it's raining (but the amount of ventilation you get is much less than a conventional side open)

@Davy90 - it's a refurb so slimline high performance. I think we'll struggle to actually achieve Passivhaus but we do have pretty big windows.

You 'just' need well installed decent performing windows then, as passivhaus is a whole building system thing and one the biggest factors in achieving it is air tightness, which for windows means how they're sealed into the air tightness layer as well as their thermal performance, which will in turn be a calculated variable in response to a variety of other inputs into the PHPP software.. (IIRC, been a couple of years since I did the course..)

For refurb, if you haven't already, look at the slightly easier to achieve Enerphit standard, if you are targeting this, airtightness is still a major consideration.. and you need a builder who understands it as mastic and expanding foam won't cut it 🙂

Check the depth of velfac. I found I couldn't fit them in my openings.

They have really good detail drawings on the velfac site. They are pretty specific on how the fit in and the details are fairly complex…

That said once you’ve got a feel for how they work measuring up is only mildly terrifying

Check the depth of velfac. I found I couldn’t fit them in my openings

125mm for DGU or 150mm TGU

@nealc - Do you mean needed to hack plaster off to fit?

@b33k34 read my post again, particularly the bit where I say 'summer purging at night' (wink)

Yeah I'd stupidly had the reveals plastered so could only accommodate a standard c70mm window.

The standard way to fit these type of Windows is to lug fix them.You screw galvanized steel lugs usually 150mm long to the outside of the timber frame pointing away from the external face of the unit.               These are fixed to the head,cill and jambs of the unit and the whole thing is fitted as a complete unit.You then fix it into place through the holes in the lugs which are projecting into the reveal and plaster over the lugs leaving no sign of any fixings.                                               External seal is provided by ilmod expanding tape and internal by Pu foam or silicone.

This is the standard method for velfac,ideal combi and rational.

As mentioned above how the windows are installed is at least as important as the window spec. Rationale are the higher spec than velfac but same company. As well as airtightness you should look at position of window in depth of opening (in line with insulation ). Also try and insulate onto front or rear face of frame to prevent thermal bridge. This will depend on if you are installing internal or external insulation. Window reveals are always a problem area for thermal bridge and require good detailing. You can’t expect to rely on the installer to detail a high performance installation for you. Some may do the airtightness but but the rest will be down to you or a specialist to detail.

So I’ve had a response from an installer about air tightness. @ajc @sargey @davy90 does this stack up or run a mile?

- use compriband and Illbruck foam (not builders’ foam) and final silicone.

-Airtight tape is an optional extra, rarely done on non passiv haus installations.

Also said they would decide on through frame or lug fix depending on survey

Through fix will depend on reveal depth and substrate behind the fixing zone.

Might as well air tight tape it yourself for the sake of a few quid for a roll of tape although this will vary depending on what you do with reveals.  The issue isn’t just how the windows are fitted, it is how you detail the reveals to prevent thermal bridging. As mentioned before, this will not be done by window installers. There are a number of ways to deal with this depending on your existing wall build up and how much mess you want to make. Pretty much no one deals with the thermal bridge around windows as they don’t understand just how much heat is lost around your expensive new windows or the risk of the reveal being below dew point. In passive house land it’s standard practice as the heat loss is understood and can be calculated . There is a lot of linear meters around every window and door in an average house.

try at eco for windows. I haven’t used them but recommend. I used ecohause Internorm for mine, they have a godalming show room. The installers were absolutely terrible although the product is very good.