George

Just a question, is it a structural engineer that said to underpin, or a surveyor?

I expect you'll need structural engineer and building control input for support of the remaining brickwork. If it's semi detached, need to have a look at what the neighbours chimney is doing because that'll affect what you need to do. If possible I think it's a lot better to completely remove a chimney - removes an ongoing liability from the roof!

Funnily enough I had my final BC inspection yesterday. The MHVR wasn't part of the original plans (hadn't decided on ventilation strategy at the start, so just sent them the BPC plans) and nor is the unfinished bathroom, so they're happy to sign off based on the completion of the extension. How would one get hold of the forum anemometer??

Just a quick update. Temperature dropped to 6C overnight and is still below 10C now. Humidity has dropped below 60% everywhere. Measuring jug filled up 500ml overnight (although some of that will be the kid's bathtime). It almost wants a 'humidity bypass' as well as the summer bypass to deal with unfavourable external weather conditions. I think next time I'll have to remember to cycle it onto low mode.

Thanks for these suggestions. 1. No the system hasn't been commissioned yet. I didn't want to do that until the last bathroom was finished, but I suppose I could roughly do it then do it again later. It's just getting hold of a anemometer... 2. Rigid ducting manifold to box and to the atmosphere. Semi-rigid for the radials. I don;t think it's been operating long enough for significant water to accumulate, though. 3. Yes, condensate drain has been attached and there is a dry/in-line trap. Although right now I have unplugged it and put a measuring jug underneath to see if anything does actually come out! There is another drain point in the expel to atmosphere duct, but that just goes outside rather than to a sewer as it shouldn't have any significant flow. 4. They're offset from the shower so the screen is in the way. Only one bathroom is operational at the moment but this is the case for both of them. I have an extract in the laundry room but have kept a dehumidifier working in there for the time being, so presumably that is sending relatively dry air up into the extract side of the system which would hopefully prevent a build up of moisture. I *think* I have passed all these checks so will assume option (1) and it's weather related. It's not a very airtight house, but wanted MVHR as I needed some ventilation and the air quality was the main attraction, so the humidity will be more strongly related to external conditions than a truly airtight house.

West Midlands. Yeah the internal temperature is only a few degrees above external but has been tipping it down all night.

Hello, I've finally got my Vent Axia Sentinel Kinetic up and running in the last few weeks. I've noticed in the last couple of days the house humidity has shot up to 70%. It doesn't feel humid, but multiple sensors agree. Prior to the MVHR being switched on, the humidity stayed within 55-60%. I've been having a think and just wanted to check my working. Is this because... 1) the weather at the moment is wet but warm. So the incoming air isn't being warmed significantly by the heat exchanger, thus the already warmish, humid outside air is getting sent straight to the rooms? 2) as there's a bathroom that's not quite finished I haven't fully commissioned the system, could there be an issue caused by an unbalanced system? Is this something to be concerned about? Should I switch off the MVHR unit (ideally no)? Thanks

Although it's not a balanced article, he's spot on at the end ... 'it would be far better to ensure that people’s houses are properly insulated first.' Trying to retrofit heat pumps in homes that aren't suitable will be a waste of money. (Of course, a well designed system in a suitable home they are great.)

Plasterboard on the inside and cement board on the outside. To hide it, either just paint the steel black or some sort of wrap around power coated flashing. . Make sure the spec of the steel paint in the outer leaf is corrosion resistant (or galvanised).

My only concern would be if the existing footing have been previously loaded by masonry and have settled due to soil consolidation. Then casting new footings in virgin soil adjacent with timber frame loading, the future settlement behaviour would be different. Dowels would help minimise any differential settlement (which is the only type to be really concerned about). But yes, agree its likely ott. But you can pay for a lot of dowels for the price of a geotechnical report... Certainly wouldn't be done for new foundations, but dowels are quite common when pouring new next to old.

Dowels into the existing foundation would certainly do the job, might even be a bit over the top. I think BC will be looking for matching foundation depths, verifying what is there is suitable (esp if trees are close by - as indicated by the the TPOs) and any special features like steel post pad foundations. I suspect as it's a bit out of the ordinary and needing to verify existing footings, you'll need a Structural Engineer and/or geotechnical engineer to provide a report or opinion.

I'd stick with 25x50 battens, but just cut 50mm stand off blocks to get the 75mm depth. i tend not to worry about small timber thermal bridges. Must admit, in a similar position I went for PIR.

A few considerations... - still expensive compared to standard construction - lead time and availability - very low density means stability (inc uplift and temporary stability) is likely an issue - possible fire rating problems - making connections - would they work with joists hangers etc? How would you connect frame cramps/wall ties - compression strength is OK, but how about shear and tensile strength - with the low mass these could be critical - while not a big issue for single dwellings, there may not be must robustness in the design - most importantly, what bank would mortgage it??

No the figures are not directly comparable. Each wall material will have a thermal conductivity (W/mK). The thermal conductivity is multiplied by the thickness and the inverse all of the thermal conductivity x thickness of the wall materials gives the U-value. A simple to use calculator is by Kingspan, but this is limited to their products. Gives you a good idea, though https://www.uvalue-calculator.co.uk/calculator/

Oh if you're using slabs then you're better off setting into cement:sharp sand bedding throughout. https://www.pavingexpert.com/pccflag1

There is a lot of seemingly conflicting guidance but unfortunately that's usually because 'it depends' In your case, you should be doing flexible block paving (assuming you are using those clay pavers pictured above) https://www.pavingexpert.com/blocks2 You need either a kerb / edging block / something solid to edge the perimeter of the block paving. These need to be haunched with a sand/cement mix, or a concrete mix. The inner blocks can be laid onto non-cementitious bedding sand. For bedding it needs to be sharp sand, ideally washed (so salt content is lower) . Jointing sand to fill the gaps between pavers.

Here you go: https://www.pavingexpert.com/blocks Best resource available on laying pavers. Used it a lot in specifying civil engineering works!

Certainly the immersion heater is wired into the Samsung control box - it uses it as part of the weekly legionnaires cycle to go up to 60C. But I've not had issues with the fan so not sure if it would. Or do you mean as a solar diverter? The supplier my installer used is 'Freedom heat pumps' and they've git a load of their training videos on YouTube which were quite interesting - was a slightly older model but functionally very similar. Ideally shouldn't muck with the settings but gives background info.

Yeah that's what I've got. Been a year of in use. Only slight issue is the energy generation calculation is unrealistically high (but energy used is fine). Zero problems with actual functionality and delivery of heat. My ufh controller is also heatmiser.

I think that's what I've got, certainly a Samsung 16kW. Let me check...

That's what I did but had decent insulation between slab and the outerleaf brickwork. The bi-fold door frame then sat on the outerleaf wall, (one brick course removed so was 75mm lower) so the inside of the frame is pretty much flush with the finished floor level.

https://www.concrete.org.uk/fingertips-document.asp?id=823#:~:text=The optimum thickness of a,for more heavily loaded floors. Is it bonded or unbonded? If bonded, then highest point of the slab + 25mm. Although if you're taking about arguing over 25mm on the height of a ceiling, it really, really isn't worth worrying about. It's a ... 1% difference.

SE solution of doubling up the joists (if the shear capacity is adequate) sounds sensible.

Carbon is only temporarily stored as wood. It does need to be released as carbon dioxide at some point (via decay or burning) else photosynthesis will stop. The carbon emissions as part of the carbon cycle are different to the carbon emissions from fossil fuels. Nature emits about 780GT of carbon dioxide every year (compared to 30GT from fossil fuels), but is pretty much all is reabsorbed via plants and oceans. This is a fundamental concept which has been part of the story of global warming since the start. Like I say, considering them as equivalent is a massive massive sop to coal, oil and gas companies. Edit -fully accept the atmosphere doesn't care about the source of CO2. This is about how you account for emissions and how we reduce them long term - the only answer is a relentless focus on fossil carbon. Also accept that sequesting biomass is a good idea. But burning biomass is also just a slow form of solar power (solar fixes and concentrates carbon, then burn it). It's the oldest and most reliable form of energy concentration.

Right, so, now you are not saying the carbon isn't released? I understand and accept the argument that there is a short term advantage in not burning biomass for our current problem. Although I've gone from biomass being my principle source of heating to a ashp back up so I'm not going to lose sleep over it. And I think you are failing to see the forest for the trees. Yes one tree took a long time to store that carbon, but the whole forest fixed a fire's worth in a fraction of the time (the whole point of coppice/woodland management. If you kept burning more than your trees can produce then you'll have a problem). Ditto for the whole absorption capability of the carbon cycle. So long as we used carbon that is an active part of the cycle we aren't going to cause much more than a few hiccups in the balance. Looking at the history of man made global warming, despite burning millions of tonnes of biomass for thousands of years, it's only when humans discovered burning fossil carbon does the CO2 levels really pick up. I stand by thinking that as a back up for a air source heat pump it is still a better solution than any fossil carbon based heating.