puntloos

Thinking slightly more modern-ly: How far do MVHRs differ in their 'HR' skills? If- for arguments sake - my networking closet actually is generating 1000W(*) - Are there MVHRs that can even deal with high(ish) speed air within reasonable pricing brackets? (I imagine the network cabinet will need some high-ish speed fans to pull that air up) - Can MVHRs deal with "1000W" style heat? Of course a powerful hob + oven will also generate even 1000s of watts but I assume that gets spread around the house as well - Assuming MVHR doesn't work, or only recovers a tiny bit, does it make sense to punch a hole in my roof/wall or is that a recipe for failure? Clearly doing it 'stupidly' will ruin airtightness and cold bridging etc etc but are there 'approved' ways to duct hot air outside? - Instead, would a secondary air-to-air ASHP make sense (or let's call it for what it is, an air conditioner)? It sounds like rather than trying to waste electricity trying to cool the air, it might make more sense to try the 'hole in the wall' approach? (*) to be clear, I plan to measure today, but my best guess of "idle" power is more like 50W - but these are 1000W amps, where that would only be reached during peak, pretty much never contiunous

Interesting stuff thanks @Adsibob and Jack - very interestig stuff. Jack - is your house anywhere near passiv? As people say apparently having air circulate is absolutely fine in passiv too so I doubt it really matters. my only exception is that I have a networking closet that is kinda hot and I can't just have that heat go out into the rest of the house.

Do you have any suggestion how I can find this? Or any sketch to give me some idea? Searched for 'architrave header vent' etc on google but no obvious thing came up. My 3D program is pretty poor at roof/wall layouts (and I'm also using it in terrible ways) so ignore any weird glitches. Obviously the skylight sits above the central hall. And yes, almost every house room is adjacent to this hall (only kitchen and master bedroom are not) I would imagine it is though, we haven't chosen that design aspect Yes, this was somewhat my idea. I wonder if they block noise sufficiently well. I think @Nickfromwales hesitated at the view of louvres but I think it could work without being too horrid. Yes, I was just wondering about that realistic balance between a passivhaus having to be 100% airtight all the time to function and just doing the 'human' thing. I'm sure venting air up is not a bad idea.

So I have a central hallway designed that goes all the way up to a large skylight. Does it make sense to have rooms surrounding this hallway 'breathe into' this hallway by perhaps creating slots in the walls? I imagine having the house's hot air trickle into the skylight and when needed opening that skylight would be a very efficient way to shed heat. Especially the plant room I imagine. - Am I overthinking things with properly designed high efficient house? - Is this idea great in summer and terrible in winter (should I perhaps make the slits openable/closable?) - In general are passivhaus style rooms insulated from each other?

My PHPP/SAP calculator guy says he needs to know 'right now' if we are heating the loft or not. He says: "If the top floor is not then heated,we need to think about insulation adjacent to this unheated space." Is this even true for a super-well-insulated house? I assume(d) that if you have UFH in G+1fl you don't even need to heat the loft?

Yeah, in my case I figure that having triple and built-in shutters is probably the way to go, but I'm with you on the bulky part. Saw one at a friend's and didn't figure it was too bad.

Helpful to know, thanks. But as an example it somewhat stands. Perhaps one way to think about this is: Which design choices yield the best cost per heating cost saved? As per your example, wall ties therefore cost 2500 to save 2.. not.. great. Of course cost saving isn't the only driver, just doing 'the right thing' (plus not having a draughty house with cold spots)..

Not sure that's fair. For perhaps the threshold design, any good threshold would be near airtight vs one with sloppy engineering, sure. But the best example I have is the Low conductivity thermal wall ties thing. Not sure they will make a *huge* difference (maybe not at all!) but I imagine a house could be properly engineered but the designer in question, not being aware these exists, would have just shrugged and chalked that heat loss up to business as usual. Sure, but there are multiple ways to get there. It's all a balance of course, you could have super expensive insulation material X with amazeballs U-value Y, or you could have a house that doesn't have that many cold bridges. Individually all these tradeoffs make a lot of sense once you point them out. But especially as a layman I'd like to do at least some due diligence on which tradeoffs even exist (because I don't know what I don't know)

Sure, so if I make all my walls and windows and doors and cold bridges out of wood I will be good? But seriously, I understand that for example while it is likely to be a good idea to have triple glazing it might not be necessary to hit a certain U value. So certainly, some decisions depend on what you need to achieve, but some decisions I imagine are probably *always* a good idea, or at least worth considering and/or checking. Is there a "passivhaus for dummies" list?

Since there is a checklist: Heating, should we not have an insulation checklist? Does anyone have one? Which design features should a house have to make sure that the overall insulation (achieved by good walls filled with sufficient insulating material) isn't wasted by a few cold bridges or other gaping holes, physically or metaphorically? A few technologies, techniques points I'm aware of: - (minor) Heat insulating wall ties - (major) Avoiding cold bridges (who will check if my house design has 0? 1? 10? cold bridges? Will a SAP calculation do it? Will PHPP show such a design flaw?) - (major) Hit sufficient airtightness levels (but which techniques do you use? Or is this a yes or no thing?) - (medium) door threshold design .. etc Does anyone have a proper list, or want to add to mine?

Ha, ancient roman technique. You have any modern implementations? In geneal I don't think I should go nuts with all technologies I could find..

You have a certain point it might not be a crazy idea to have a separate system, but like I said my office kind of has a direct air duct to the loft so while 'ducting across the universe' has some downsides, it feels having an ancillary aircon (ASHP?) right next to my plant room on the roof might not be crazy

Thing is, I'm indeed struggling to picture a sensible way to indeed think about the location of available water of both hot(ish) and cold(ish) varieties and where it makes sense to add/remove heat from it. Does anyone have some sketch on how this works? For one I do have a hot and a cold buffer planned, so presumably I could perhaps try to heat the hot buffer with hot air (probably via heated water with @SteamyTea's A2AHP point? Actually - https://www.hidros.eu/uploads/ART/1LZTP4/BRO_LZT-P4_ENG.pdf - ok, it's a bit beefy - 25kw - but the size is "sort of okayish" - 2000x1500 footprint. And it's fairly noisy I think. (but it's far in the garden..)

Actually this one - https://www.gledhill.net/products/alternative-energy/stainlesslite-heat-pump/ - was already my top choice. Same type of idea it seems. But this one takes fluids for the coil (aka 'warm water from the heat pump') - I think I'm missing some type of extra device to collect energy (heat into the water, or electricity) from the hot air?

I wasn't aware you could do this with warmish air. Do you have a link for a device that does this? Or is it effectively a "chiller coil" but running in reverse? Hmm. So you would put the dehumidifier.. in the cabinet? Or somehow inline with an MVHR? It's a good point to air seal the office door. I'll make a note of it. What type of independent system are you thinking of? FWIW: As you can see the service riser goes through the entire house, so I might just be able to pull the hot air up to the plant room and potentially exhaust towards the skylight if I'm really desparate. But indeed some optimized way to not have the heat go to waste would be great. There will be a chiller coil near, so perhaps it can do some useful work?

I doubt it . Even the lightest device that you could consider a PC (a chromebook) does something like 30-45W. Either way, both my projector and my PC certainly are thirsty, even though they are modern. And no I'm not bitcoin mining or something like that.

Actually this is a LED projector ? I'll certainly be looking to minimize, but my desktop PC by itself runs at 550W when gaming. Then I rounded up for a few of the other pieces bits and bobs. Certainly the PC won't be on permanently, or gaming even when it is on, but you have to take peaks into account not just averages.

Well I guess it's the 'something useful' part, right? I'm sure that I can pull hot air from somewhere relatively easily, but now do I use it? I'm not quite seeing how a humidifier helps? Well, since the house is near-passivhaus-level I'm not sure that excess heat is not going to be a problem? Even in my current 'standard 70s' home, just my PC running a game very clearly increases the heat in the room. If we can spread it around the house, maybe that would suffice? Frankly the math here is too alien for me for now, not sure where to start digging in to how (e.g.) a 8kW ASHP can handle 1KW of actual heat generated? Obviously it sounds like it would easily work but I'm sure reality is different?

To my mind there are a few spots in my house that will generate a lot of heat for a low amount of volume. - Kitchen Oven and hob, obviously Probably (?) okay to not do too much fancy stuff beyond a few MVHR inlets - Projector enclosure in Livingoom 400W projector that needs to be sealed, at least in the front (into the livingroom) for noise reasons - Networking cabinet in Office This is the big one. Network switches, home automation, a powerful PC and suchlike might hit 1000W heat generation in a 600x600x2000 box It's in the office, but bordering the livingroom. > Do I feed direct cold air into it, or should I just pull air from the room? > Do I pull air out with MVHR? I suspect I need a special high-speed air pipe? My main service riser is thankfully very close, so a big pipe is doable but noisy fans are not.. (can I have some device in the loft suck the air rather than push the air in?) - Plant/Utility room in Loft HWC prob not leaking too much, but MVHR device KNX boards, smart home control stuff ASHP endpoint For all of these, it would be great if a MVHR could, well, 'recover the heat' and somehow use it wisely, but I understand that a MVHR really doesn't capture that much heat. What do? Install a simple split AC into the loft that will just pull heat in and out of the hot air inlet and put it into the cold air outlets? (yes I have an ASHP too, at that location, perhaps it can actually handle the hot air? Duct the hot air outside? (sucking the house vacuum doesn't seem ideal ... ) More powerful MVHR that can handle meaningful heat spikes? Can I store the captured heat into the hot water cylinder or is the recovered heat really not worth "doing stuff with"? Leave it all be?

Just a note here that I found these fan coils: Carrier Idrofan 42EP - 156mm (oops, not 150..) in-ceiling fan coil. https://www.carrier.com/commercial/en/fi/products/air-treatment/hydronic-terminal-units/concealed-and-ducted-fan-coil/42ep/ http://eto.carrier.com/litterature/sdd/7579247.pdf

But what about the mutated flying elephants? As I understand it we need to aim for 2.5-5% incline, and yes, was planning to have that coating too. I'll see if I can get away with an openable skylight for access but perhaps it's overkill

A decent idea. No I don't really intend to clean them myself if it requires any sort of skill to not die. :)

Here's a few things to avoid -

Just out of curiosity, of course a rope and hook shouldn't *just* be able to hold say 150kg (assuming our average builder isn't that obese) but also the strain of such a 150kg load falling straight down for say 1m first - short drop and then a sudden stop, as a matter of speaking How do you spec this out? What is the actual requirement on such loops and ropes? Do you have any tips (URL?) for what type of harness and rope would be needed?

I was thinking that, yes. But is that OK for the english regulators?