ICF heat loss calcuation using JH sheet and deciding to give PHPP a go

[Muellar]

Hello

It’s been a while since I posted as we’ve been busy with design updates, as well as being busy working to save money for a new build!

I’ve also been reading articles here (thank you all) as well as doing my own attempts at calculating loads as there’s quite a mixed view and now I’m in a position to share what I did in the hope that maybe it’ll be helpful for someone else and to discuss on this forum.

 Some key figures about the house are:

1.        New build ICF on a hillside outside Antrim

2.        Nearest weather station is Aldergrove but I adjusted for exposed site

3.        Zinc/Ali clad for 30% of the perimeter then timber cladding for the remainder

4.        Total NIA is 290m2 and habitable (excluding garage and plant room) is 243m2

5.        Internal volume is 946/822m3 respectively. It’s large as we have a few vaulted ceilings to make the most of the views out towards Lough Neagh

6.        There’s 186m2 of external walls with 91m2 of glazing

7.        U values I’ve got are walls will be 0.14, floor 0.13 using TLA, vaulted ceilings/roof is coming out at around 0.1 and windows will be a mix of DG/TG – DG purely for sliding doors due to weight

8.        Will install UFH with an ASHP, maybe GSHP as there’s a lot of digging anyhow

Using the spreadsheet provided by Jeremy Harris I got a total heat loss of 6394 watts.

I then went a decided to buy the PHPP software to learn more, and put in all the data needed. That took a lot of effort and I had to fiddle the windows section but that came up with a lower figure so I’m having to work through it again when I get some free time.

The profile from PHPP looked right however, max heating in Jan/Feb/Nov/Dec and correlated with what a couple who built an ICF home in the area back in 2019 have found with their GSHP.

Here’s a copy of the PHPP losses profile:

The initial PHPP results are coming out at 28 kWh/(m2a) and a heating load of 15 W/m2 which was arrived at from a max total of 65.7 kWh/(m2a) which was then reduced by solar/internal heat gains of 38 kWh/(m2a).

I need to spend more time on this PHPP sheet to ensure I’ve got it right as the figures just seem too low, and I’ll do that when I get the time.

We are now producing the necessary working drawings and will get the electricity load calculated on the basis of a 7kW heat pump unit.

[Russell griffiths]

Why double glazed doors as opposed to triple, weight shouldn’t be a reason to discount a product. 
My triple glazed sliders were 400kg plus, I’m very glad I didn’t pick double glazed in stead. 

[Nickfromwales]

18 minutes ago, Russell griffiths said:

Why double glazed doors as opposed to triple, weight shouldn’t be a reason to discount a product. 
My triple glazed sliders were 400kg plus, I’m very glad I didn’t pick double glazed in stead. 

Sales persons think the simple sale will be the quickest sale. 
Simples. 
These people have overheads to cover so cannot go a month with no sales caused by their integrity. 

[Conor]

Your house spec is near identical to ours. 9kW heatpump and it works perfectly. You want a bit of headroom as the as-built performance will never be the same as the model. In theory our max heat load is just 5.5kW. BUT, we run our heatpump on economy 7 about 90% of the time and the entire house is only two zones, and it works well. It only needs to run 20hr/day when it's really cold, so about 2 weeks a year.

 

Fyi we have 5m x 2.7m 3G bi-folds from feneco. No excuse for DG sliders.

Edited October 27 by Conor

[Muellar]

@Russell griffiths @Nickfromwales DG/TG conundrum is really down to weight and value for money on the extra cost of TG against benefit gained. We will decide when we get quotations. Should be easy for a supplier to give us both once they've got the sizes and type entered.

 

@Conor being in tropical Co Down you've made me think about resizing up our heat pump as we'll be up on a hill outside Antrim (210m above sea level) so it'll be a lot cooler than where you are is my guess. I thought i'd accounted for this but your comment re running it for 20hrs has made me think... we were going to have a wood stove but removed that, now I'm wondering! In terms of the glazing thanks for the comment re Feneco; the largest sliding doors we'd have would be 2.3m wide, we've got a few sets of them.

[Nickfromwales]

That’s all good.
Doors and windows are a relatively permanent feature, so buy cheap buy twice is my advice.

Heat loss argument is instantly outweighed by how draughty shitty-quality doors/seals/locking gear will become when they begin to fail with use, so that is where I’d focus my attention when buying.

I’d favour bifolds over sliders every damn day, as you can almost fully open up the….opening.

A reputable supplier will sell reputable gear, so don’t buy these from the middle aisle in Aldi   

[JohnMo]

57 minutes ago, Nickfromwales said:

Heat loss argument is instantly outweighed by how draughty shitty-quality doors/seals/locking gear will become when they begin to fail with use, so that is where I’d focus my attention when buying

We went through the pain of this on our build. We ultimately travelled 60 miles to the companies main show room, and nearly every window/door on show had a defect, either the handles or seals were not doing what they should etc.

 

Ditched that company and uPVC all together. Moved on to better, but more expensive unfortunately, but as @Nickfromwales says, once installed they should be there a long time.

[Muellar]

@Nickfromwales@JohnMo sound advice and is what i've done previously, it'll be intersting to see the relvative cost difference between D/TG from the same supplier, that is where I'd be looking at the pricing in detail than purely going for a cheap set of windows.

 

Interesting comments on bi-fold v sliding. My head was in the place that sliding would be more water/air-tight than bifold (fewer moving parts/less seals etc).. Your 'bifold over sliders every damn day' has got me thinking.

 

Just to give you some context, we have 3 main large openings. Main bed = 5.5m, Kitchen/Dining/Lounge = 8.4m and Rear onto patio = 4.4m. Our SE has managed to design in a beam so the 8.4m opening can be clear span.

[JohnMo]

13 minutes ago, Muellar said:

3 main large openings. Main bed = 5.5m, Kitchen/Dining/Lounge = 8.4m and Rear onto patio = 4.4m

Big openings, hope you have done something to manage thermal gains from the sun. You may fry with low spring and autumn sun.

[Muellar]

23 minutes ago, JohnMo said:

Big openings, hope you have done something to manage thermal gains from the sun. You may fry with low spring and autumn sun.

I did wonder about that JohnMo, however the PHPP came up with no issues on overheating when I put in the stats for natural ventilation and as we're on a hillside outside Antrim we can readily open up and ventilate - fly screens needed!

 

I'd seen more benefit from the heat gains in late autumn/winter/spring than a risk on overheating given location (temp/wind) and the limited days of sun/warmth we have. lol

[JohnMo]

Good you've looked.

[Muellar]

40 minutes ago, JohnMo said:

Good you've looked.

I should have added that I the main bed will have a balcony so the windows are quite set back, same for the larger 8.4m so we'll also look at practicalities of shading as we get more into it but I guess you can only design so much out/in.

 

Not sure if you saw my original post when I joined, but we've got these windows all there becuase of the view out over Lough Neagh. We did toy with reducing window area, but we felt we'd just ruin the point of building where we would be, and thermal gain/overheating was on the top of my worry list. But great that you mentioned it. Thanks.

[JohnMo]

4 minutes ago, Muellar said:

but we've got these windows all there becuase of the view out over Lough Neagh. We did toy with reducing window area, but we felt we'd just ruin the point of building where we would be

We are in a similar position on a hill over looking a Loch, we have loads of glass also. We use UFH in cooling mode and it effective in knocking the thermal gains down a bit, but importantly reduces the recovery time to normal temps, quite quickly.  It not Aircon, but effective enough, for no cost.