Matthew GarrettWhen something is described as "Heats or cools (x volume)" how do I interpret that if I live in an area where the extent to which I want to heat or cool the space is on the order of a few degrees rather than a few tens of degrees?
Andy Wootton@mjg59 It's meaningless without knowing the rate you are losing or gaining heat from/to the house, which obviously changes with the weather and season. I started with external insulation to get the flow rate down and the units were equally unhelpful. The 'experts' pay for computer models they don't fully understand from organisations like PassiveHaus.
@woo sigh yes all of these numbers are meaningless but how do I translate one number into another given the assumptions made in the original number, which are theoretically consistent given all vendors use the same system
Tobias Petersen@mjg59 @woo This is actually one of those times I really like working with an AI. Getting it to look up some common assumptions and defaults to check if they match my own guesses before making some back of the envelope calculations.
I could do that myself but digging around multiple sites and PDFs to verify gather spread information it does much faster than me (and it's easy enough to verify some of the sources when it has found them to ensure it hasn't made the numbers up).
jarkman@mjg59 @woo I got a new air conditioner yesterday, so this set me off looking for whatever standards the vendors might be using.
I failed to find them, though. I think in the US there are two, DOT and ASHRAE, which give you different numbers.
My adventures in building energy measurement have taught me that nobody ever knows (or has a good way to measure) most of the important parameters of their building, so it's all of a bit of a crapshoot anyway.
Sorry none of this is helpful.
@jarkman @mjg59 My memory has a bullet-in delay: I think the terms were 'thermal insulance' and 'thermal conductivity' (lambda value) which I think is the one defined in terms of the heat loss through the area of an infinitely small point and 'multiplied up' to per square Metre but you can ignore all that for a heat pump. It needs to balance 'the energy you lost through your energy bill' and I was told a heat pump can only keep up and be economically viable if your rate of loss is already low.
@mjg59 I didn't get as far as the heat-pump. None of the people I met who fitted external insulation had a clue about the theory. They just follow 'industry best practice', which might not be.
@mjg59 Obviously energy bills give you the data on the rate your home loses energy, if you aren't going to change anything but we were.
I actually changed the windows first. That made the walls damp in the bathroom and kitchen, so we open the windows in Winter, until we improve ventilation :-(. Good luck!
I recommend a set of humidity monitors to understand your 'moisture profile' now, ideally for a year. I bought cheap ThermoPro with a phone app. I assume the heat pump will de-humidify?
I actually changed the windows first. That made the walls damp in the bathroom and kitchen, so we open the windows in Winter, until we improve ventilation :-(. Good luck!
I recommend a set of humidity monitors to understand your 'moisture profile' now, ideally for a year. I bought cheap ThermoPro with a phone app. I assume the heat pump will de-humidify?
earbs 💖💛💙@woo @mjg59 this is something to watch out for when sizing a/c - if the cooling cycles are too short it will cool but not dehumidify; if they're too long it will dehumidify too much. inverter compressors and sufficiently "smart" systems might me able to mitigate this now?
a couple jobs ago the facilities folks installed one n*2 BTU a/c instead of the two redundant n-BTU ones requested. to run enough to keep the proper humidity, it ended up holding the server room at something like 55°f.
when moving equipment out of the server room we had to put it in a garbage bag first, then let it sit bagged outside the door until it warmed up to the point the outside humidity wouldn't condense onto it...