Temp

Our system has a thermal store that you can dose with chemicals. The DHW is heated by a heat exchanger. So none of the water that comes out of taps is stored for very long.

https://www.bbc.com/news/science-environment-65339934

Served or agreed?

If you actually prefer the single storey now.. you could also say... if you don't agree the new PWA on same terms without surveyors fees I will build the two storey.

I would follow the instructions to preserve any warranty. I've read that packers should really be flat so they support both sheets of glass. Otherwise the weight of one sheet is supported by the seal. Any drainage holes and channels should be kept open to stop water collecting innthem and freezing in winter damaging seals.

I'm not far from the River Nene and its been high for most of thus year do far I think. A few fields flooded until recently.

My understanding is that there are both positive feedback (runaway) and negative feedback mechanisims (stability). These have caused and stopped swings within a range that has kept the Earth broadly habitable. The problem appears to be that rapid increases in CO2 can over power the negative feedback mechanisms leading to wider swings. No not because it got hotter. We didn't get runaway then because the sun wasnt quite as bright and CO2 didn't increase rapidly. The feedback mechsnisims were able to keep up and eventually prevent much higher temperatures. I think of it a bit like inflation. We can cope with 17% price rises over 10 years without the economy suffering. But 17% over a year is a much greater problem.

The issue is humid air inside the office (due to breathing, plants, cups of steaming tea etc) finding it's way through gaps in insulation to cold parts of the timber frame where it condenses causing the frame to rot. The standard book ways to avoid this are as you say... vapour barrier on the inside and ventilate the cold side of the insulation. The problem with just drilling ventilation holes is letting rain, bugs and mice in. The holes really need a grill on the outside which might be difficult given proximity to the fence etc. The would also make quite a mess of the appearance. Venting the roof at the ridge might also be problematic. I think I'd probably take a risk and not bother to ventilate the cold side. I might paint everything with a wood preserver and when dry fit a Rockwool like insulation between the timber frame and a rigid PIR on the inside of the frame so sheets are butted together. Tape joints and fit a plastic vapour barrier as well. Do a really good job of the vapour barrier. Hard to quantify the risk though. Beware, foil covered insulation may well block your mobile signal and WiFi. If you want power in the shed get an electrician to do it. Perhaps tell him to fit a small "Garage CU". Surface mount wiring to avoid big holes in your vapour barrier.

If you enter a post code here it takes you to your councils Web page if they have one. I suggest entering a nearby post code not your actual postcode then navigating if they give you a map.. https://www.gov.uk/apply-work-on-protected-tree

Not in a conservation area are you? If you live in a Conservation area you have to act as if all trees (with a trunk over 6"? ) have a TPO on them. TPO can also be applied to all trees in an area rather than individually. Some councils appear to have an online database.. https://www.medway.gov.uk/info/200147/applying_for_planning_permission/128/applications_for_works_to_trees/2

Either way you should not press the membrane against the underside of tile battens as dirt and water can collect above the batten causing it to rot.

No I mean water loss from the screed makes the screed weaker not the slab below the insulation. Water also reduces the insulating properties of the insulation. Our builder even covered the screed with a temporary plastic sheet as soon as it could be walked on to stop water loss into the room by evaporation.

The key to making sealer last is to stop all movement. If the bath moved when it's filled with water and you get in then the seal won't last. It doesn't have to move much. One reason for the suggestions above to fix a batten to the wall. Check the floor under the bath. Chipboard can bend or worse when wet. While the bath is out perhaps put a layer of WBP plywood down to stiffen and or repair it. Also make sure any adjustable metal legs are solid. Sometimes they use nuts which can come loose allowing the bath to move. When you think it's rigid use a pencil to mark the top of the bath on the wall then fill it with water and stand in it. Does the top of the bath still line up with the pencil mark?

Deleted.

I believe the one on top helps stop water loss from the screed making it weaker. Something like that.

Might be worth checking out any implication for the CIL. For example a self builder can only claim the exemption before work starts on site. I'm not sure if demolition is considered starting. It's possible that demolition might save them stamp duty but hit them with the CIL. There should be a common sense solution but the CIL rules don't cover a lot of common situations.

Think I'd cut blocks of PIR and use expanding foam to fill behind/around them.

This. If within 2m the whole building must be under 2.5m https://ecab.planningportal.co.uk/uploads/miniguides/outbuildings/Outbuildings.pdf

+1 I think it should be mandatory to fit cavity closures when windows are replaced if they aren't already present. Go at it with a can of expanding foam but be careful as it's easy to over fill and push off external trim. Do a test first as it can carry on expanding for a fair while.

Found this although I'm not sure the way they calculate averages is correct. Should be weighted by the number of houses in each age band? It's also worrying that for detached houses it seems to have gone up after 2006? https://tools.bregroup.com/heatpumpefficiency/dwelling-heat-loss

Historically electricity has cost roughly three times gas on a per kWH basis. So it's important for most people that the average COP is more than three or running costs will go up. Can that be achieved with 60-65C flow rates? The other problem is the size of the heat pump required. According to this web page... https://www.boilergrants.org.uk/news/how-much-gas-does-a-boiler-use The average gas boiler in the UK is rated at 35kW. It's claimed that lower output ASHP can be used by running them for a higher percentage of the time. But the same argument can be applied to gas boilers. I wonder if we really have enough data about the "load factor" of gas boilers in cold weather?

I did ours back in 2007 and found this guide useful.. https://electrical.theiet.org/media/1695/electrical-installations-outdoors-a-supply-to-a-detached-outbuilding.pdf Hopefully not out of date.

Is the top shaped to form a cavity tray?

Just make sure to fit pipe inserts.

We replaced a big flourescent with the 120cm version of one of these in our utility room. Plenty bright enough for us. https://www.amazon.co.uk/gp/product/B07WMMLJFZ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1