Windows in a sips

[Taff]

So we’ve had our windows in for a while now, all have been fine until the colder months have arrived. We have a sips build and used aluminium frames. The windows have been installed into the stonework and not the frame! Is this correct?

 

reason why I ask is the frames have excessive moisture where I need to wipe them with a cloth. I understand the frames will be colder due to the material but the moisture is pretty bad. I’ve only just rigged up the MVHR so hopefully this will help. 
 

I feel if the frames were within the timber there would be less of an issue.

 

house is extremely warm so that may be an issue and hopefully MVHR helps 

[Gone West]

Ideally the window frames would be installed inline with the insulation layer. Presumably the aluminium frames have a thermal break in them. What is the RH value near the windows. We have single glazing in one window and an air temperature of 23C and RH 50% near it and we dont get much condensation on that window.

[IanR]

Have you got a section showing the window position in the wall?

 

As much of the frame as possible should be across the insulated cavity to avoid a thermal bridge. If the window frame is mostly in the stone skin such that the thermally broken half of the frame is in contact with the stone then you have a difficult problem to fix. The internal part of the frame will be at the same temp as the stone and you will get condensation unfortunately.

[ProDave]

You mention aluminium frames.  Is there a thermal break in the frame or not? do you have any specifications or drawings of the frame construction supplied by the manufacturer?

[Taff]

@Gone WestI’ll dig out the spec of the windows I would hope they have a thermal break! I’m afraid that I’m just picking up the pieces of rouge builder and rubbish architect ?. I best get myself a hygrometer to measure.

 

@IanR I have a feeling that they are installed incorrectly by the window company! See pic best one I got on my phone.

 

@ProDave I’ll dig this out after a cuppa ??

[Taff]

@ProDaveThe website states they are thermally insulated 

 

With low uv

[LA3222]

Can't quite make out what's going on in that pic. My build is SIP, 50mm cavity then rendered block. I installed timber pinch battens all around the openings and lined them with some insulation so that the windows weren't in direct contact with cold wood in the cavity. I got the window installers to put the windows in so they protruded effectively approx 20mm beyond the pinch battens so they lined up with the sto e cills. Can't recall the frame depth off top of my head but if I have 70mm sat beyond the SIP frame there is probably at least 70mm again sat in the SIP frame.

 

Another thing to consider is your house may be drying out still. I had bad condensation issues last Xmas and had to wipe the windows daily. The MVHR wasn't on then and because the house was so airtight it was a PITA and I had to get a dehumidifier in to bring the humidity down.

[IanR]

It's not that clear from the photo, but does look like the window frame is 100% in line with the stone outer course, so the only thing insulating the inner half of the thermally broken frame from the potentially cold stone course is 5mm - 10mm of expanding foam.

 

If this is correct then while the window frame itself is thermally broken, the stone course is creating a thermal bridge to the inner half.

 

It may be made worse by high RH while the building dries out, but I would imagine this will still be an issue later on once the building is dry. To confirm this you could get an IR thermometer and check the temp of the inside surface of the frame when it is cold outside. If it's dropping below 12°C it's likely to cause condensation.

[SteamyTea]

Is this a new build that is drying out?

If so, the problem may vanish in a few weeks.

Edited January 2, 2022 by SteamyTea

[Taff]

Purple is the window 

Red is the void

blue is the sips panel 

green is plaster board 

 

it looks a bit thicker as we put extra insulation internally 

 

it is a new build but we’ve been in 10 months! How long does it take to dry out

mvHR has just been installed in the last 2 days 

 

 

[saveasteading]

8 hours ago, IanR said:

If the window frame is mostly in the stone skin such that the thermally broken half of the frame is in contact with the stone then you have a difficult problem to fix. The internal part of the frame will be at the same temp as the stone and you will get condensation unfortunately.

I am thinking that is a reality of a window in an original stone wall. Otherwise the window has to be inset and the reveals will get wet.

So it is a compromise, and a weakness in the envelope. But is there any solution?

In the context of the whole building, perhaps the heat-loss through the inner skin to foam, to stone is no worse than through the thermal breaks themselves, which are just short lengths of plastic.

 

[LA3222]

25 minutes ago, Taff said:

Purple is the window 

Red is the void

blue is the sips panel 

green is plaster board 

 

it looks a bit thicker as we put extra insulation internally 

 

it is a new build but we’ve been in 10 months! How long does it take to dry out

mvHR has just been installed in the last 2 days 

 

 

Your windows are sat well forward then, so younhave the cavity open to the interior, I suppose there are two options, bring the windows back or insulate/seal the cavity off.

 

Surely the cavity should have been sealed/insulated with cavity closures etc before the windows went in?

[Gus Potter]

1 hour ago, saveasteading said:

I am thinking that is a reality of a window in an original stone wall. Otherwise the window has to be inset and the reveals will get wet.

So it is a compromise, and a weakness in the envelope. But is there any solution?

In the context of the whole building, perhaps the heat-loss through the inner skin to foam, to stone is no worse than through the thermal breaks themselves, which are just short lengths of plastic.

 

Sorry for the OT post but maybe you have a rebate you can work with.

 

When you have old solid walls it's a challenge. Your starting point here is look at how the wall is constructed. In the late 1600's the weighted sash and case window caught on for houses but this was high end stuff at the time. Have seen some steadings that have sash and case but the steadings were subsiduary to the main house so some Lairds were not that keen to share the luxury with their "workforce".  There are steadings ( folk lived in part of them) and buildings for housing animals (barns / byres ). Sometimes you just have no rebate especially if the wall is 14" instead of 20" thick. The key here is that to fit a sash and case window they created a good rebate behind the rybats and lintel. The rybat is the stone up the sides of the window often looks like a key effect from the outside.

 

Now with modern windows (even a sash and case window) you have space here to be innovative. Modern sash and case look alike windows are often fitted with spiral balances instead of pulleys and weights leaving you room to play with to get some insulation behind the window frame and up to / against the rebate. You do need some discrete fixings which act as a thermal bridge but.. you can't have all the cake..

 

 

 

 

 

 

[Taff]

On 02/01/2022 at 17:52, LA3222 said:

Your windows are sat well forward then, so younhave the cavity open to the interior, I suppose there are two options, bring the windows back or insulate/seal the cavity off.

 

Surely the cavity should have been sealed/insulated with cavity closures etc before the windows went in?

Yep that’s what has happened they have sat the windows beyond the cavity and the cavity’s are closed not sure why they did this, I wasn’t involved in much of decisions at the start that’s where things have gone wrong, I’m no builder but surely fames should have been positioned inside of the cavity, perhaps the timber structure would cure some of the coldness on the frames. I’m beginning to think we should bring the frames inwards ?

[craig]

I would, architect error or install error. Very little thought on the warm line and is going to end up with moisture and possibly mould.

 

Check the 1:5 section drawings for window position. Check if you signed these off, if not put it back onto the architect. If drawings show further inwards. Put this back to the supplier.

 

In a SIPS kit I like to install halfway in the panel or on the outer edge of the panel. 

[Taff]

@craigcheers I will look into this tomorrow it clearly is correct ??