JohnMo

Run separately, you may get interference

That is stainless steel cleaned up with something that has been used on carbon steel, a grinder for example. The normal engineering way to get this off is with an acid gel. Not something you can safely do at home. The stainless is not rusting. The carbon steel deposited is corroding. A local engineering shop may be able to treat it for you.

My GSE trays are mounted direct to sarking boards. You may loose 2 to 5% performance of the hottest day, very little or none at other times. Our sarking boards are normal Scottish ones 22mm thick, approx 150mm wide. Trouble is, if the put the battons as per instructions, but on top of the sarking boards, the slates don't install very well.

But the tank would have pressurised from a tank in the loft, and had really bad flow all of 3m head (less piping losses) in an upstairs bathroom.

Speak to different structural engineer? Or challenge the one you have. Ours wanted all sorts of steel in our walls, until I challenged him and then he dropped the requirements considerably and to far more what you would expect. Trouble is they take the easy, low risk for themselves approach, because it's easy and requires not thinking out of the box.

Durisol are an easy company to deal with, their block also easy to assemble. 4 weeks, ready for roof, two of us who had never done it before. 70m long wall, 190m2 floor. Front of building approx 4m tall rear 2.5m

Don't think most plumber (there are exceptions) do anything different from what was done in 70s. They still plumb the same way, no reason to change, as no one asks for anything different. Very few use hot and cold manifolds for example, which distribute hot water more evenly

Have been on to the two companies websites and downloaded the installation instructions, they include all the approved installation schemes and the expected u values. It tells you where you need air gaps and what depth they need to be etc.

You could also inject some CT1 or similar, before taping

Get a magnet, if it sticks it very very low grade stainless or carbon steel. Are there any bolts or screws near where you are seeing rust, if they are not stainless they will corrode very quickly and stain the stainless. These should be replaced with stainless unless they are structural. For painting, clean with soapy water, grind surface clean, clean with soapy water, flush with clean water and dry. Use a multi surface primer and top coat. Same approach used for galvanized also.

They are designed to provide a fixed temperature for any given flow, winter water temperature are lower than summer, and manufacturers install a flow restrictor on the water inlet to give year round ok performance, an increase delta T is required in winter; due low cold water temp being lower. Flow when inlet water is at its coldest is rubbish compared to summer, the restrictor gives worsening summer flow also. With a flow restrictor installed flow will be down 10 to 15% on advertised rates. However as with most things they tend to follow the path of least resistance, so open a tap and flow is diverted there instead of the shower. So could be a couple of reasons for the rubbish performance Plumbing arrangements giving biased flow to the outlets closest to the boiler. Shower mixer not responding to change of flow of hot water. It should be an adjustable TCV, so manage the temperature set even with flow changes. So flow rate reduces, not go cold/hot. The easy fix on new build, manifold to individual users. For new or old systems Canetis Superflow on inlet and removal of flow restrictor. This give s 30 deg inlet temp to boiler, giving improved flow. Shower mixer that control temperature not just rate of flow for hot and cold.

Ask for a meeting your you planning department. Go over the details with them. This should be just a maintenance issue, once you have listed consent, not a change - so no planning needed

MEV allows multiple extracts to a single outlet. In that case you ventilate the wet rooms and possibly the ones with no other ventilation. The inlet flow would then come window trickle vents and cross flow through the house. Or go dMEV, these have a fan in each wet room and have always running, low energy fans, with boost from light switch or humidity sensor. Put through wall vents (on internal walls) in the unventilated rooms. For this to work you need an air gap at the bottom of all internal doors. You window trickle vents work as MEV. Best to draw your house layout, look at where to have air going out already, where you have air coming in (window vents etc) and then can make a guess at where the air flow to and from, and see what room have no ventilation. Ventilation wants to go across a room where possible.

Been living in house for the a couple months with MVHR, and still can't get over how quite it is. Especially when you go to the toilet, put on the light, no noisy fan starting up, just quiet.

Why not Durisol, they are made in Wales, easy DIY, or they could advise local builders. Come pre insulated and give an out of box wall u value of 0.14. Wet plaster finish will give you airtight walls. They are also have plenty of standard details for block and beam etc. to reduce thermal bridging. With rest of your details and 200mm insulation in floor, an easy to achieve very well insulated house.