All Activity

Have you priced up Frametherm 32?

@Novice what is you normal heat system - ASHP?

When inside is hotter than outside. That is the only time.

Bypass mode, as it's name suggests, bypasses the heat exchanger. In a hot summer, that will result in HOT outside air entering via the mvhr with no cooling effect. Leave it in normal mode. Then outside air that is hotter than inside, will be cooled by the cooler extracted air. I have struggled to find any time when it is actually advantageous to use bypass mode.

We have been living in our certified Passivhaus since it was completed in August 2017. It's a relatively large house (approx. 400 m²) and overall has proved extremely comfortable and energy efficient. However, in recent summers we have increasingly experienced overheating in the main living areas. Despite using night purging and running the MVHR in summer/bypass mode, there are periods when we struggle to bring the internal temperature back down. We are therefore considering installing a couple of air-to-air heat pump/split AC units – probably one serving the main living area and another on the top floor. My main concern is maintaining the integrity of the Passivhaus airtight layer when installing them. The wall construction is shown in the attached drawing. The airtight layer is 12 mm SmartPly/OSB on the inside of the 300 mm twin-stud timber frame, with a 38 mm internal service cavity before the plasterboard. Obviously the installation will require refrigerant pipework, condensate drain and probably cabling to pass from inside to outside. I don't want an installer simply drilling through the wall and filling around the services with expanding foam. Has anyone installed split AC/air-to-air heat pumps retrospectively in a Passivhaus or similarly airtight timber-frame building? In particular, I'd be interested to know: How did you detail the penetration through the OSB airtight layer? Did you use proprietary airtight service grommets/collars or tapes around the pipe bundle? Is it better to install a larger airtight sleeve through the wall and pass all the services through that? How was the sleeve/penetration dealt with at the breather membrane and external cement board? How did you deal with the condensate drain without creating an air path? Would you pressure-test the house again afterwards to confirm the airtightness hasn't been compromised? I'd be very interested to hear from anyone who has done something similar, particularly on an existing Passivhaus.

My bad, I meant bats - currently looking at Nyrock 32 and have a decent quote from SIG that is almost £2K cheaper than a cellulose quote I've had! So the pir I mentioned is 1.5K cheaper than the bats, and they in turn are almost £2k cheaper than cellulose (waiting on other quotes).

I just want a second opinion on the below as the implications are significant and I'm struggling to understand the proposed wind posts locations and also the excessive amount of ladder reinforcement at 225mm centres. The internal block leaf is 7N medium density.

Yeah, I have a bad feeling about that. The information available is scarce, with some mention of them being made for 600mm centres - but then pictures show then boards as being 600mm wide! I'll see if anyone local has them...but even then, I wont know if seconds will have something different.

Agree, but that's not what I was responding to. We have been somewhat talking past each other. I responded to you saying the UK is a good example of decarbonisation and that by extracting more oil/gas we are risking that. My response is that while we have achieved a significant reduction in our emissions, a significant proportion of that is because we decided (intentionally or indirectly by actions) to just stop doing a lot of high carbon things. We aren't a good example of transitioning existing industry to low carbon, industries in this country are shutting down because they can't operate in our business environment*. Other countries have done a much better job of that. Talking about Burberry and Mulberry is a distraction. They are relatively small components of our economy that are not generally replicable. * Mainly it's electricity/gas prices (which we could have addressed in a different way) but it's also a general complication of rules over the last few decades (and Brexit) that adds friction. When other countries have adopted holistic carbon reduction schemes that encourage and support companies through the transition with active government support (and in doing so have achieved some great results) and we don't, we really can't claim to be a good example.

We’ve gone fancoils upstairs and UFH downstairs. Dual zone setup on Ashp so we can run the fancoils with proper chilled water in hot temperatures. Hoping we will be in in next few months and will report back in summer if it works!!

Decarbonising doesn't mean stopping - merely removing (where possible - see pt 2). There are plenty of industries which burn gas and sometimes oinnthat can switch. Paper making, brewing, wood work and countless others use steam. Often generated by a gas boiler. Those processes can be replaced by electric heating - they can even be replaced by heat pumps in some situations. Secondly, there will always be some processes that just require gas (or oil or coal) normally because they are being used as much as a chemical feedstock as for heat (or even entirely as a feedstock). These processes will have to remain as fossil fuel consumers - it is net zero not absolute zero. Aviation is a classic example. I cannot see long haul aviation get away from fossil fuels for quite some time. We would need to have a significant surplus of electricity to begin to start making sufficient quantities of synthetic fuels (I don't think bio fuels from current farm practices will cut it). But my point was that industry changes all the time due to different pressures. Energy prices are part of the mix but probably don't affect a bespoke sports car maker as much as skilled labour and parts availability. I don't think Burberry and Mulberry are as bothered by the price of electricity as they are the availability if leather and skilled leather workers (and probably most importantly the whims of international fashion)

This is correct, thanks Rick. The heating and hot water work well when the ASHP is running. The issue is that the ASHP randomly cuts out and flips into immersion mode. Given that immersion mode never gets above 20 degrees, it's effectively useless at that point. It kicks back in after I restart the system. The installer annoyingly put the main controller in the garage next to the tank - always fun being out in my dressing gown first thing in the morning So my Ecodan set up should (I think) have the water on permanently. It's set to heat to 50°. It then has a 10° drop off before kicking back in, and presumably going back up to 50. That seems correct because when it's working, the water is rarely below 40° according to the MelCloud (Mitsubishi) app. I'm not sure how to manually check the diverter valve but I'm pretty sure that's fine too as the heating works well when the ASHP is running. Hmm, so very frustrating.

Then for the same u value use a decent high density mineral wool batts.

Not required if you use a combined/directional inlet outlet. One of our two MVHR units is in the middle of the house, the two ducts effectively go in void above built-in wardrobes to the outside wall. Our manifolds are in the same void. But it only feeds two bedrooms and extracts from two bathrooms.

Thanks.

The tray goes on top of the flashing, discharging any water onto it.

With the mvhr you do need to get the 5 or 6" supply and extract pipes to an external wall and around 2m apart. Plus all your ducting. So its not quite as easy as popping in a cupboard. I'm not trying to be pedantic its just these do take up a bit more room once you allow for connections. Have to be strategically placed too.

Got me thinking how does a flashing interact with a dpc tray? By grinding a lead flashing into a course are you not sending water behind it if running off a doc tray?

I've no experience of the boards, but if you have 600 mm centres in your roof, then the gap to be filled will be less than 600mm and you'll have to cut a small amount from the width of every board.

kWh Thermal inertia is what you need to be looking at. https://en.wikipedia.org/wiki/Thermal_inertia

I'm hoping to have our roof built next week, using 600mm centers and was looking at blown-in cellulose or mineral wool - but budget is getting tight! I was having a look on seconds & co and so this size of boards which in theory should just slot into place. Does anyone have experience with these pre-cut strips? (I'm looking at a saving of just under 2K)

Just about to start insulating a timber frame one storey rear extension. It'll get about 180mm PIR in walls and ceiling and 75mm in floor. So that's nice and warm. But, - the existing house - from the nineties has a cavity wall with 140mm AAC on the inside (meeting building regs back then - and kind of ok) but brick on the outside. The cavity is not insulated, and during the work on the extension work it was clear there's a strong breeze going through that cavity. So come winter I assume that will be as warm as a single skin brick wall 🥶 - and do anything it can to cool down the extension. Any ideas on how to insulate that outside - but now inside - brick wall - or how to close the cavity behind it to stop the breeze ? Thank you so much

>>> Asking for opinion will yield a possible or negative reaction depending on the experience of the person answering. If you want a thin screed vote with your feet and do it Yeah, appreciate that. I'm just trying to get my head around the building physics and its dynamic behaviour. I get your very good point about the heat flow direction based solely on the difference between floor and air temperature. And the 'heat flux' i.e. quantity of heat transfer should presumably be about the same as the 'thermal resistance' between the floor and air should be similar in both cases as the interface construction will be the same. That leaves the speed at which the heat pump can replenish the 'radiator' and whether the quantity of heat in the radiator will be drained fast or not and whether that is significant. Where is @SteamyTea when you need him? Maybe I should just say KwH or something to wake the genie up?

Maybe that's why I reacted so badly to this one. I remember getting stung inside my nostril a few years ago whilst cycling and it was a sore one but not that bad. I was thinking maybe this time was worse cos I was already awash with histamine from the barley stubble I'd been walking through all day (I'm not allergic to many things, but barley is one) and the numerous nettle stings I'd picked up at the fencelines. I probably couldn't have picked a worse day to wear shorts.

My father was severely allergic to wasp stings. I have never wanted to put it to the test as I have all sorts of allergies. Apparently some people react normally to the first sting, then can get sever reactions to subsequent ones.