G and J

Tuck, our air fryer, has proven itself invaluable, but like his fictional namesake he is a wedgie one so takes up a lot of space in me pantry. So I’m going for a combined fan oven/air fryer. Methinks all an air fryer is is a powerful fan and a nicely powerful heating element.

Well, whatever I calculate my ASHP will be a bit too big and when I light the fire none of the calcs will even start to be relevant… And so from my point of view I’m not sure I care what figure I should use in Jeremy’s spreadsheet as long as it gives me an approximate answer to the ‘how close am I really’ to passive house standard. Maybe I shouldn’t worry. Maybe it’s better to travel in hope….

My oven is likely to go below worktop. It’s not used that much and it’s not that hard to use in that position, and I am someone who’s knees are such that I have issues getting into the back of our under counter fridge. I think oven cleaning is harder when the oven is below worktop - but one could always use an oven cleaning company or get a self cleaning oven or both. My microwave will be a standard one in a cupboard. Cheaper and easier to replace, not in show and I like hidden, and when I’ve talked to sales peeps they’ve been cagey about whether a combined oven/microwave is as good as a simple stand alone microwave.

So the lowest external temperature is 4.8C so if I plug that into Jeremy’s spreadsheet my heat load is nicely less than 10W/m2 so I’m building a passive house after all. Good job. Where do I hang my certificate? 😉

Obsessively Virgoan Disorder. Do keep up! (or maybe V just happens to be next to C on a qwerty keyboard and I need to clean my glasses again lol)

Not sure if he’s OCD, but that’s wonderfully neat work. To be very highly commended (yes of course my long list of neuroses include OVD -I’m a Virgo!)

Most importantly @Nick Laslett are you happy with the finish? And was the cost of having tape/jointing/FST done very different from a traditional skim?

In my experience self employment suits some but not all, and there’s a good few different aspects to that, including: vulnerability to income anxiety; need for social interaction; aptitude for organisation and admin; level of personal confidence. I personally don’t believe everyone is suited to it, but I do believe that if one is suited, it's easy to underestimate how hard others might find it.

(Given that the service was good in the end…) what overal u value did you get with those doors?

The trouble with answering a post like yours is that I pretend to myself that I’m being objective but in reality I can’t help unconsciously putting my personal preferences forward. So be warned….. but… If I’ve understood correctly the main bed faces south east, and the end gable of the single story bit faces roughly north east, i.e. the direction the sun come up in in summer. I’m with Nod on making the single story bit double, and I’d be tempted to use it for a bigger and more luxurious main bedroom with a really nice sized bathroom and dressing room. And I’d face the windows (plot and planning allowing of course) towards the morning sun, with the bed facing the windows. (Oh look, I’ve just described our build lol) It’s lovely that you appear to be giving your kids so much room but fast forward to when they’ve their own families and you may find that layout means you are cramped but not using a large area of upstairs. I’d price up putting steel in so the wall between kitchen and snug could be removed (which would be a lot cheaper if you did go two storey above the snug) to allow reconfiguration of downstairs later as your needs and preferences change. And I’d allow for plant somewhere (not the loft), maybe a decent sized cupboard.

As if by magic, the answer appears…..

Don’t be. I’ve probably learnt more on here from diversions than direct responses - it’s the lifeblood of a forum methinks. Fab. Do you happen to know if the results are comparable with PHPP? If not then I need to be careful how excited or depressed I get!

I guess I want the formula behind the annual heating demand row in your spreadsheet.

Very interesting and useful stuff @MikeSharp01, thank you. I’d grasped the principles of load vs demand but it’s details like TFA and perhaps a rough and ready calc method I was seeking to get a feel for how far short of passive we will end up being. ’Near passive’ is a term used on here but I am interested in quantifying how near. Maybe I’d be better of not knowing and staying deluded lol

I thought my heat load as measured at -10c and with 148m2 of floor is 2500/148=16.9W/m2 which is not so good compared to the PH target of less than 10W/m2. I was also hoping to be able to calculate what I think is called total heat demand which is measured in kWh per m2 per annum. Maybe I need to raid me piggy bank to buy a PHPP license to find out, but as it’s only of passing interest I was hoping there would be a way of deriving a credible estimate.

Fab discussion. Very illuminating. But I still don’t know how to calculate total heat demand. 😞

Agreed, but I didn’t want to assume that the heat load calc assumes that too.

Our MCS plumber dude told us straight of that the smallest heat pump we can have will be oversized, so I kinda took that as a given but corroborating opinions are useful. I was trying to calculate heat load/demand to get my head round how far off passive standard we are. With the current set of assumptions I’m working to at -10c the heat loss divided by the internal floor area is around 17W/m2, so we are well over. At the Norfolk level of -2.3c it’s 13W/m2 ignoring DHW - and just over 14W/m2 if I do the patent @JohnMo 24/22 DHW fudge factor - which doesn’t look so bad after all. My confidence level in these numbers though is not high yet as I have the queasy feeling that I’m missing a basic, partly because they are so much better than I naturally expected (I still associate passivehaus with long straggly beards and 4’ thick cameldung and candyfloss walls, but then, I am an old reactionary at heart!). Heat demand though still confuses the life out of me.

Ta for the link - won’t let me register at the mo but will keep trying.

So, guess who has been up late googling..... I found the following on an Australian website (I think it still works even though they are upside down over there): "While the building heat load tells you how high the boiler output needs to be, the heat demand indicates the amount of energy that is required per square metre over the course of a year. The heat demand or building energy demand is therefore a criterion for describing the energy quality of a building." Makes perfect sense. So if i look at Jeremy's spreadsheet it calculates the heat required to maintain the internal temperature - default is 20c inside and -10c outside which gives me ~2.5kW. But.... I'm not sure if -10c is excessive for Suffolk, There's no allowance for getting up to temperature, and There's no allowance for hot water either. And I'm really not sure how to derive the heat demand figure from his spreadsheet. Help!

Brilliant link. Thank you.

I’ve filled it in and I continue to play with it on a ‘what if’ basis. And yes, I’ll be very embarrassed if both figures are there already and I’ve failed to notice! (But I’m ready. I’ve my own conical ‘D’ hat and a stool waiting in the corner!)

Dear Buildhubbers, I’ve been trying to find a formula to estimate our house design’s heat load and heat demand, but the combined intellect of google and me have failed. Please can someone enlighten me. Regards, Confused of Suffolk.

In previous lives (well, when I was working) I encountered no end of folk who knew their calculations were correct and relevant because they had a spreadsheet that calculated numbers to 3 decimal places, or the like. So I’m with you on that one. Often an informed guess beats the calculator.

That’s certainly my impression. If you look at the engineering involved they should be less than £100 a pop but the volume isn’t there yet.