Ed Davies

Using PVGIS and assuming azimuths of 100° (10° North of West) and -80° (10° S of E) gives 48.5 kWh and 59.9 kWh for December and January respectively so your 50 kWh/month looks pretty reasonable. That's for a point at the southern end of the main runway at Sutton Bank (Yorkshire Gliding Club) which will have a pretty clear horizon from east round through south to west. It seems to me that 1.5 kW would be a bit optimistic with the low sun and the awkward angle on to the panels. Still, 200 W does sound a bit disappointing. (Does the “T21” in your name have any gliding significance?)

Yep, ordered one last night.

I can't visualize how a blending valve could be set up for the UFH loop but with the towel rail running at full temperature without having separate pumps for each circuit. Alternatively, what about wiring the towel rail and UFH in series so the towel rail drops the temperature a bit then the rest goes into the UFH?

Won't that need annual inspections and all that stuff?

Without an expansion tank, where would the water expand to as it warms up? Why wouldn't the tank burst? Or crinkle up as it cools down?

There's blocking at the end of the joist, two bits vertically between the chords which are held in place by those crimped-on spiky things. Just wondering if they were done at the factory or on site.

OK, thanks. But was the blocking crimped on on site or at the factory?

@Alexphd1, were the bottom cords cut to length and the blocking crimped on on site or at the factory? Did you do the rim boards then give them mm level measurements, or what?

Any chance of taking studs up to the roof? Perhaps 1.2 metres from each end.

I have a few, none of which is satisfactory. A little electric stapler/brad nailer which would probably be fine for furniture stuff running off mains but hardly tacks at all running off either my inverter generator or 1200W inverter - I assume it takes too large a pulse for the inverters to ramp up and give the necessary power. A little Powerfix (Lidl) one which would again be fine for furniture. An Arrow one bought from the local builder's merchant which looks appropriately chunky but usually doesn't drive the staple right in to membrane/OSB, though a quick tap with the hammer sorts that, but worse jams a lot and is a pain to take apart to unjam - have to take off a small nylock nut. Not a happy thing up scaffolding, wearing gloves in failing light. So @Cpd's Stanley looks very tempting. OTOH, I'll need a second-fix nailer too fairly soon so a cordless brad nailer/stapler might be a better bet. I find that it's best to staple two handed with the Arrow stapler as otherwise squeezing the lever can pull the staple emitting bit away from the surface and suspect the same might be true of the Stanley. Not a problem in ideal circumstances but reaching into awkward corners, etc, can make that a bit tricky. So a one-handed electric one might be better. Still, the Stanley's quite cheap so worth having in the tool box, I suspect.

The nail doesn't go through a joist hanger, it just curls back on itself. That's trying with 51mm nails in a Paslode IM360 nailgun. Yeah, I experimented. Cautiously. Wearing thick gloves and safety glasses (I do all the time anyway as I need the bifocal bits). About half way through the doing the various twist nails in my frame. Almost exactly the same number as Russell (5280 for the roof and floor plus whatever in the gable walls).

Membrane can be under the counterbattens. As designed mine would be: 1) Rafters (JJI I-beams) 2) 150x22 treated sarking boards. 3) Membrane. 4) 12x38 treated counterbattens up and down the roof, over the rafters and nailed through to them. 5) 38x50 treated battens across the roof. 6) Profile steel sheeting. (Actually, 1-4 are done but the membrane has failed so I'm planning another layer of membrane over the counterbattens). Putting insulation between the battens would be a bad idea. The purpose of the gaps is to allow ventilation and to allow any water that gets under the outer rainscreen (tiles, steel or whatever) to run down. Water can get there by being blown by wind from odd angles or by condensation on the back of the rainscreen. Apart from marking where the rafters are for future nailing the counterbattens' main purpose is to allow air to get up past the battens and water drops to run down the roof. If the battens were nailed direct to the sarking or the gap between the counterbatten but under the battens was filled with insulation then water running down the roof would be dammed by the battens leaving them permanently soaked. Even treated wood won't stand for that.

If you want to know a bit more about battery chemistries there's worse ways of spending 12 minutes than watching this:

There are probably other things which can be used as a precedent for this. E.g., rainwater harvesting systems.

I don't think much sag is needed to allow water past but perhaps somebody who really knows can give advice on the wisdom of putting in insulation which might push the membrane up against the battens.