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humblebee hive - retrofit #3

Updated: Mar 23


So exciting: finally met the team on d-day: Richard - retrofit coordinator - Chris & Erol (Team "Windows") and Tim & Liam (Team "External Wall Insulation") and the Green Building Store "Performance" windows arrived on the back of a wagon just over two weeks ago.

Definitely time to replace the windows...

First day on site (also our home, and kids were still on half term), bin collection day and we quickly realised we hadn't really thought about parking. We can get 4-5 cars in front of our house at a push, but it doesn't leave any space for delivery of materials, and when Richard is here that's a 6th vehicle (when you count ours). It's residents' permit only in our cul-de-sac - so we scrabbled around asking neighbours (thanks folks!) for the loan of their drives and any guest permits, as requesting them from Cheshire East is a lengthy process.

Anyway, we had coffee, sat round the table and discussed the details one of my collaborators and fellow Passivhaus designer had sketched for us so it wasn't all just "finger in the air" type stuff... Suddenly a whole load of questions arose, especially over how the external shutters (Souh West facing bedrooms) were going to be supported, and no, we still didn't have a design from our social enterprise joiner I'd commissioned to come up with something.... Cue sleepless night: visions of half the wall being pulled down, especially as it was the week after 3 named storms had literally battered our South West facing elevation.

But it's all good: the windows arrived late morning, and although it was heavy work for the team to manoevre them off the pavement - wagon driver didn't feel confident reversing onto our drive (?) and round to the back, the day proceeded with good humour. We hadn't managed to clear out the garage - even after various attempts - but the windows were fine to be left outside, we were assured (and so it transpired).

The workers seemed happy enough and had an action plan so work began in earnest - starting with a car and van ballet - early on the Monday: trench digging for the French drain was on the menu for L & T, and fitting the first window (our bedroom) for E & C. It was fascinating for me to see the tools and products that made up these four's arsenal. What impressed me though was their attention to saving every last screw and finding uses for random bits and pieces. It was also nice to know our old French doors were going to be used in a garden office project. I knew we'd found our tribe and it certainly inspired confidence.

1. "Team windows" 2. First window out 3. There's a hole in the wall! 4. Externally painted for longer warranty RAL 6021 (Pale Green) 5. This one and the landing window were single glazed originally (brrrr...) 6. Natural finish on the inside - our old patio doors had a second home to go to (yay!)

Team Windows quickly whipped out the panes and frame from our main bedroom window using stanley knife and crow bar mainly. But the dimensions were going to be too tight - so having measured that the sill would still be 800mm high* (just), they'd already decided they were going to take a brick course off the bottom. Sounds onerous but in fact they did this with ease, and it ended up being a feature of the whole job.

R delivered us lovely quality plywood and E&C set to work on fixing it as a box to the new window frame: the purpose of the ply box is to position the window within the external wall insulation layer to minimise thermal bridging. What we have come to appreciate is the lovely deep sills and window seats that have been created as a result.

It was nail biting watching them manhandle the 1.8m x 1.16m triple glazed window - with its 10-ply box now attached - up the stairs (averts gaze after a while) and then, with the help of Team EWI on an access tower, into the opening in the wall. It takes a long time just to do that operation. And it's so physical, they manage one window a day: nothing like the 2-days tops for modern double glazing installers. To be honest, that suited us as we had to clear the space in only one room at a time - LOL.

Getting the first window in was no mean feat!

Airtight foam, a silicone airtightness seal and airtightness tape will keep the installation virtually infiltration free. An 8mm ply lining, edge architrave and a window board will eventually finish off the surround.

Gaps in the CWI (!)

Opening up the wall allowed us to see the cavity insulation, which we realised had a few gaps in it at the upper level (between the two injection points), so it was just as well we spotted and rectified those - all the more important to check those CWI fills with a thermal imaging camera (we must have missed it somehow, or the temperature contrast between inside and outside wasn't high enough that day, or just didn't know where to look).

Liam and the porthole window

Every day a new window, some deliveries and plenty of light hearted chatter and music - maybe it's the effect of 2 years of pandemic and lack of social interaction, but it's such a joy to have this enthusiastic team around.

Next post: fun and games with the groundworks and I have a go with a trowel!

*any window below 800mm needs to be specified with safety glass.

Costs #3

Triple glazed, timber framed windows (includes some aluminium sills), Green Building Store £12,810, VAT £2,568 Total £15,378.

Window Survey, £240; Installation, £6,415

Total Windows: £22,033.

Total retrofit to date: £26,433 (approx. £240 /m2 GIFA).

Glazing U-value (Ug, centre pane): 0.575 W/m2K, g-value 0.53.

Average overall window U-value (as calculated by PHPP): 1.03 W/m2K.



It's me, hi!

Welcome to my blog where I download some of my latest thoughts and musings, talk about experiences, write up my biggest personal project - my own home retrofit - and generally use it for catharsis.

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