Sparrowhawk

Hard to measure the impact as it's warmer outside this morning than yesterday so is the 2C difference due to that or no hole in the wall, but the lack of air movement in the kitchen is noticeable.

The deed is done I had to wait until the weather warmed up to be above the "min 5C" temperature for the foam, and used a disposable Soudal can as the straw it came with was small enough to fit through the air brick holes without drilling them out. It took the whole can to get it to seal this plus back to the airbrick so I imagine the cavity has a bit of fill too.

Hi @Alan Ambrose Do you know why they're failing? Is it water being blown in between the frame and sealed unit that's reacting with the glue? Air pressure making the glass flex and breaking down the seal? Given the size I'm thinking the latter is most likely, but photos of the edges of the next one that fails would be helpful. Not answering your question, but when I asked on this forum about sealed units someone gave me https://www.sealedunitsonline.co.uk/ I also found https://www.glasstops.co.uk/ which has a bigger range of glass.

Hi @pyros and welcome to the forum. Congratulations on the impending arrival - you've got a well-positioned new office planned to ensure the noise won't disturb you! I am surprised no one has picked your post up as you've provided good detail. I suspect because of the forum you've asked in, but let's see if this 'bump' to the top gets you some feedback. I am very amateur and still working through my udnerstanding of what BC require for retrofits. My only comment is about your planned layout. Why put the bathroom at the far end of your office, rather than the end where you have planned french doors? My thinking is that having it there, with a corridor past the bathroom and then an entrance into your office makes the bathroom more accessible from the rest of the house. Yes it messes around with where the garage door replacement needs to go, but in terms of living with the finished house it seems more practical.

The width is 890mm. Measuring up the side of the window reveal is 14cm to the edge of the Velux frame / 18cm to the pivoting window. I am curious what's in there, might have to drill an inspection hole and have a look.

Our kitchen with the hole in the wall has 2 very cold north-facing windows about 20 years old. While outside looking at the airbrick I also had a look at these windows for the first time since we moved in and spotted a few gaps. Window A The one below isn't bad at least there's plastic at the back of it (unlike window B) Window B The gaps at the top should be foamed/caulked I think, but the one at the bottom where the window doesn't sit on the sill? Is this a drainage path and so shouldn't be blocked? Under the sills of windows A & B Under the sill there's some gaps in the render. Hard to photograph but again something I could fill & seal or is it a place water will drain away?

Did you get anywhere? I am pretty sure I have air leaks too but Velux technical services are impossible to make see reason.

That's my experience when using a 30cm extension tube with Soudal Flexible Expanding Foam Gun Grade. It changes the texture of the foam and it doesn't skin over in the same way. I think this way which you and @ProDave have suggested is the most practical approach and most likely to succeed. The outside of the house is rendered so the air brick can be rendered over eventually. Though I must take the tape off the air brick tomorrow and check the two line up!

The expanding foam cans I've used (gun-grade & not) have to be held near-vertical to work. Is there one that will work on its side under the units?

Here you go From the eaves on the en-suite side of the room, it will be 100mm air gap and 50mm PIR, and then plasterboard. But here I would hope there's PIR against the wood forming the window surround. And then more given the depth. I don't want to strip off the plasterboard when other places are far colder but it is on my list for "maybe one day"

I am struggling to get a measure of whether it is or it isn't. I haven't got a blower door made yet so I'm reliant on strong winds in the right direction, and the weather's not been cooperating. It could be a cold spot. The 19th was another cold day and this time I opened the windows. I wanted to see if the condensation stopped at the rubber seal or went up the frame alongside the pivoting bit containing the glass (whatever that is called). At the bottom there was the bigger patch of condensation again. I am satisfied these are cold bridging. Here, the condensation stopped at the line of the rubber seal. All along the rubber seal position was a line of condensation but it didn't extend above the seal. Fair enough. At the top corners the condensation went up further all the way to the external seal (the rubber gasket round the pivoting bit comes at approx 1/3 of the height down the white frame here) There was also frozen condensation further up in the window To me the fact the condensation doesn't stop at the seal says there is an air leak at the top corners. Whether I can make Velux understand that the condensation isn't the problem and what it shows is, I doubt it. It's a cavity walled house. I'm under strict instructions not to post photos of the bedroom in its "lived-in" state, but this room is in the 2001 extension and in cross-section is a triangle with its top point cut off. The roof extends to floor level but they put a little stud wall up to hide the end part (no idea what's behind that). The wall to the left is 2001 cavity, filled with either sheet polystyrene or mineral wool. The wall to the right is the original 1920s external wall, empty cavity. To get the radiator to work properly in this room you have to turn the radiators off downstairs to force more water upstairs. It gets to 13.5C max atm, and then we don't have the heating on in the morning until one of us goes down to turn it on. We will get this sorted when the new heating system goes in. Velux are right that the condensation should disappear with a lower RH, but to my mind the condensation is not the problem but a symptom of another problem: cold spots and maybe air tightness problems.

Another weekend, another hole...

I know, and yet I hesitate because of the cables in the wall. There's enough views on this forum ranging from "it's going to be okay" to "you're an imbicile to even consider it" that... I don't know. So I push on with other measures and delay making a decision fo what would be one of the biggest wins for insulating the house.

It's draughty at foot level in the kitchen so I took the kick boards off. There were a couple of bits of wood piled up in the corner which I hooked out with a hammer. On the outside there is an air brick at this point (single clay brick size) so I was expecting something. But perhaps an airbrick with a grille that I could tape over. This is an all-electric kitchen, no gas appliances. The bottom of the hole has plastic sheet on it (damp proof course?). I tapped the top of the hole with a hammer. The top is thin plaster. It's taller than it looks. How am I going to seal this up? It's behind a corner fitted unit. Lying on the floor it takes my outstretched arm plus a 15" hammer to reach the closest edge of the hole. I can't take the bottom out of the kitchen unit as the fixings holding the carcass together are on the outside butting up to the neighbouring units. Is cutting an access hatch in the bottom/back of the kitchen cupboard the only way? And then the best approach to cut PIR board to fit and tape the edges? Bonus question: is this how the sink waste is meant to be secured into the drain?

Velux have responded. Oh dear. My message to them, photos removed as same as above And their response:

Why's that? Aren't boilers sealed units venting to the outside only?

As scrap car radiators fans on ebay seem to go at a premium at present, would one of these 12" fans or these 16" fans be powerful enough to do the job? They're listed with the same CFM so I'm thinking the smaller one.

I need to stop being a parsimonious ***e and get one of these to try. For that kind of money have you considered a good quality backdraught shutter instead? The Naber THERMOBOX is the only one I've seen and thought "that's well engineered" about (I asked for other recommendations at https://forum.buildhub.org.uk/topic/30851-back-draught-shutter-recommendations/) but with an inline fan it'd be worth an experiment to see what it would do?

I need (okay want) to get an IR camera but I do have an IR thermometer. After wiping the condensation off the bottom part of the frame on both windows, that part measures 7.5C. The rest of the frame up the side of both windows measures 9.5C-10.1C (close to room temperature). These sides are butting up with the roof construction which is 50mm PIR between rafters. My guess for the bottom section is the installer hacked back the PIR too enthusiastically and didn't foam up to the window. Could be the same at the top, but the Velux foam collar should've dealt with this I'd have thought.

On my windows the trim strips are glued and caulked into place. My approach is to use a Stanley knife to cut through the caulk (trying ever so hard not to slip and cut the UPVC window frame) and then get a scraper underneath or even a chisel to loosen an end. After that the whole strip can often be ben upwards and the now-brittle glue breaks. If you need new ones (can you fix it so they're no longer required?), my approach has to been to stick them with caulk or silicone sealent in place. Easier to remove next time!

Re trickle vent that's a really good point. I knew I'd seen this kind of condensation before on a frame, and that reminded me it was when I left a trickle vent open (on other windows in a previous house). Welcome to my story Last night the windows were shut in the bedroom & en-suite, but I married a woman who likes a cold bedroom, so (until today) the heating's been off in there. And the ceiling mounted extractor fan in the en-suite lets a draught in. Mind, by morning the rest of the house was 9-11 degrees so yes there's serious heat loss / air infiltration going on.

The wooden frames we replaced never had condensation either. Though being 20 years old and never revarnished the frame had split and the previous owner had removed the seal between sash and frame so they could still be opened...

I've been unable to track down the makeup, their brochure says: Thermal transmittance window Uw 0.92 - 1.0 Thermal transmittance glazing Ug 0.5 Energy transmittance g 0.47 The other Velux we had replaced in the Study has had ice on it all day long.

I thought so! Velux said (direct quote) "The seals look fine" when I raised this.

We had two new Velux UPVC windows fitted in November 2022 and went with the 62 glazing as top of the range. Codes: GGU PK10 0062 with BDX PK10 2000 When -1C/-2C outside we've had condensation on parts of the frame, and I thought they had slight air leaks at the top. So I got the installer back who said "nothing to do with me" and raised with Velux Technical support. Velux technical support have said that "Condensation is an environmental issue, there is too much moisture within the room. You have used BDX collars so we know the window has been insulated properly." Photos from today The room was at 61% RH at 10.2C this morning. -1C outside according to the Met office, feeling like -6C. In the top 4 corners, we get corner condensation on the frame. This is where I thought/think there were air leaks, assuming that was cooling them down: At the bottom on both sides of both windows, for 8 inches up from the corner we get condensation: The glazing gets some condensation round the edges of the entire window, but I was expecting that (triple glazing isn't a miracle, right) So... Is this normal/expected? If it was too much moisture within the room as Velux say I'd expect condensation around more of the frame, not specific areas. As a comparator we had a third Velux replaced at the same time in a different room in the same aspect. It's a cheaper GGU PK10 0068 with EW PK10 6000 and has no condensation issues (but is in a room we don't sleep in). RH in that room this morning was 54% at 11.1C.