JohnMo

We had a very small hidden leak, which dripped once every couple of hours, we got plenty of mould by the time we spotted it. Localised humidity will have little affect on the total room humidity and would not trigger the humidity sensor.

We used fibre reinforced concrete

I'm going to using 3x2 concrete slabs cemented in place.

My option is and it could be wrong. Any small gap water will settle, the smaller the gap, then more capillary action will hold it there. Give mould half a change it will take hold. I would say it needs to be grouted or sealed in someway. The only thing if the sides of the tile are glazed that may help, if they are not, they may absorb moisture and make thing worse. Doing nothing, may be a high maintenance finish, needing plenty of cleaning.

How well insulated is your house first as it makes a big difference.

Sory got my numbers wrong it is 100 global companies are responsible for about 71% of all CO2 emissions anyway? Oil and coal equate for most of it. There is always a flare, on each offshore production facility and each refinery which will be circa 0.5 to 2 mmsfd (million standard cubic feet a day) in normal running conditions, in upset process conditions could as much as 40 to 50 mmscfd or even much more. Offshore production will also have power generation of 30 to 40 MW by gas turbine driven generators, 1MW on a drilling rig which will be diesel powered. So not that small.

MVHR will not spread the heat around effectively, you can still have very hot and quite cold areas, you are doing less than 0.5 air changes an hour.

Carbon neutral should work, CO2 produced to generate, equals measures to remove the same amount of CO2 from the atmosphere. In reality that means, you take statistical data, you manipulate the inputs and outputs to meet your own political wants and needs, exclude things like airports and air travel, and anything else you get political pressure from or is really difficult - then you get carbon neutral. Doesn't really matter what you think or voice your options about, that is the reality of government. Isn't it 7 global companies are responsible for about 80% of all CO2 emissions anyway?

If the tree has fallen over of a branch has fallen off, that would rot naturally and release CO2 back to atmosphere. If using this work you be closer too carbon neutral, but anything taken down to burn, just released loads of CO2, so not carbon neutral. I did consider going the same route as you and just settled on a normal log stove. To save complication. You really need a thermal store to make solid fuel work, but they may not be best for ashp. I did see a German stove that could directly connect to an UFH loop to spread the heat further, but was huge money. Trouble with the connection scheme they show for the combi is there is no storage for the hot water, once you light the fire most your house thermostat will switch and you will just be dumping heat. If your house is well insulated, you won't have the fire on for long without melting yourself. We have a single stick on at a time for about 30 mins.

According to data sheet it should be fine for floor and soft wood https://www.rockwool.com/uk/products-and-applications/product-overview/fire-stopping-products/acoustic-intumescent-sealant-en-gb/?selectedCat=downloads

Need to fill all gaps, and tape them. The screed will weight it down. You don't want the screed to under the insulation or that's a world of pain. Prior to UFH heating pipes cover insulation with thin DPM and tape all joints.

If the scope is for the contractor to complete, ask him how he intends to complete the scope. If its not his scope get someone else.

Why have loops in hall and utility, there are tonnes of pipes going through that space already. As Dave says your corridor is in the centre of the house, it will borrow heat from elsewhere. Strongly suspect the hall and utility will suffer from overheating, as designed. Would not have UFH pipes under beds either. For the time it takes I would download loopcad of free trial and review the design yourself. You tell Wunda sell pipe! Have considered 200mm pipe spacing? Are you having electric towel rads in bathrooms? For summer drying. If I was doing it again I would do electric UFH in bathrooms.

Huge and bulb replacement, means scaffold to do it safely. Think carefully how you will maintain once furniture is in place. Low level up/down lights work well and are maintainable.

You may find any warranty is void if not bonded with the correct adhesive on a concrete floor with UFH. Read the manufacturer installation instructions, for whatever make you are choosing, there will be a defined method. Our clearly stated that.

Do you have room at the top of the roofline to install external insulation instead, a single layer of 120 to 150mm, would be easy to install and give better u values.

Have a look at the kingspan website that should give you some ideas. Plenty of companies with solutions.

If you are really concerned why not look at coanda effect nozzles.

We have a smart electric meter - keep being asked for meter reading or get estimated bills, there a complete waste of time.

Recirculation for me. No they don't all have carbon on filters, some do come with, others its an option. There are two types of carbon filter, use and bin or regenerative. Mvhr will do a good job of smells and steam, just put on boost. I don't bother with the extractor if it's just steam, if frying or very smelly I use the extractor and mvhr on boost.

Not mad. If you can get the best insulation you can, get much better than building standards. You would end up with house that cost next to nothing to heat. I found with both companies if you go too custom, the price goes up dramatically. Using their standard designs, with optional best insulation, would give you the least stress. Knowing what you want is key, get a list together of wants, early, prior to tender. Wide door, level threshold at all entry exit points, all showers with completely level entries, all ensuite accessible etc. Don't get carried away with room sizes, go around show houses, see what suits you, measure up

Emmisivity without an air gap is next to nothing. So the foil would act as a conductor anyway.

If you want UFH you need a well insulated slab. A U value of about 0.15 or better would be your target. That would require a minimum of 150mm PIR. Without that you will be pushing too much heat downwards and it will be expense to run. To make running costs of an ASHP viable, the house needs to be well insulated. An ASHP will convert 1 unit of electricity to 3 of heat, but that unit of electricity cost 5 times that of gas. I would do the following Insulation aim for u values of 0.15 or better everywhere. Airtightness Electric or dual water/ electric towel rails, in bathrooms to allow towel drying in summer. Possibly electric UFH in bathrooms, so it is quick to respond and you heat only when needed. Revisit gas move costs, do you need to move meter or just reroute pipes? Look in to MEV with heat pump (link below) or similar. This may have advantages if your house is not airtight. The balance of the heating with IR Radiators, or A2A heat pump. https://kers.co.uk/kers-mev-landing

I did mine very early in the build process and used fibre reinforced C34 concrete.

Aluminum reacts with the alkalis (OH) found in portland cement concrete. When these two chemicals are combined, the reaction produces hydrogen gas. ... corroding the aluminium foil, but mostly causes bubbles in the cement