SIPS v ICF - is Phase shift really a factor?

[Muellar]

Hello

 

I've progressed a house design using ICF, but got concerned at all the detailing so that various things could be installed - from boxed/hidden blinds to fixing of heavy items - and this made me consider SIPS as an alternative.

 

My gut feeling that having density/mass in a build was a good thermal buffer and then reading through various items on BuildHub I found out about decrement and then UBAKUS so I inserted various build profiles to see what the results came out based on a base SIPS option i've seen and then adding 45mm of cork to the outside and finally an ICF build up I like.

 

The benefit of SIPS over ICF now looks to be on the increase I'd get on the internal floor area, with a fixed external allowance, as well as ease of future fixings for what looks to be a marginal benefit due to the difference between the increased phase shift that ICF gives when I look at the temperature difference on the inside surface.

 

Have I got this roughly right or is there a better way to look at this? I have included screenshots of the output from the software for the 3 main scenarios i've considered.

 

[JohnMo]

Decrement decay is real. The other issue is noise transfer. SIPs are quite noise transparent, ICF aren't.

 

Are you comparing similar U Values?

[SteamyTea]

Taking those modelled phase shifts if 7.2, 10.3 and 12.5 hours only really apply on the 2 days a year when each hours of daylight, or hours of darkness, coincide with the phase shift.

The other times the building is cooling or heating.

Did you just model a wall?

The two biggest influences are the glazing area/orientation and the uncontrolled ventilation rates.

A thermally inefficient floor can have an impact as well.

The footprint area to perimetry ratio makes a difference to.

 

Basically once out of the tropics, daylight hours plays a larger and larger harder game the greater the latitude.

 

The UK also has a strange climate, not easy to model reliably as we can have warm nights in the autumn and winter (last week was over 13°C), but quite cold in the spring. Much of this is to do with the sea surface temperature around the UK. It is this relatively high winter SST that makes the UK cloudy.

 

 

Edited 11 hours ago by SteamyTea

[Alan Ambrose]

I never understood this either - is it better to have a 12-hour delay (so the phase shift partially cancels out the temperature driver) or as long a delay as possible (so the inside is as unaffected by the temperature fluctuation as possible)?

[Kelvin]

It’s better to reduce the extent of the glazing. However we bought the plot for the view and full height windows are nice feature in my opinion. Most of our south elevation is glass so the temperature in those rooms varies a lot more and more quickly. The temperature in the other rooms tends to be a lot more stable and consistent. As always  it’s a compromise. 

[saveasteading]

3 minutes ago, Kelvin said:

Most of our south elevation is glass 

Because I've been looking at garage doors, I've come across several external rollers for windows. They are not as expensive as I had assumed considering they are oitdoors and motorised. I can vouch for how effective these are in Mediterranean weather, keeping sun out in summer and heat in, in winter. 

[-rick-]

9 minutes ago, saveasteading said:

Because I've been looking at garage doors, I've come across several external rollers for windows. They are not as expensive as I had assumed considering they are oitdoors and motorised. I can vouch for how effective these are in Mediterranean weather, keeping sun out in summer and heat in, in winter. 

 

Just had a quick google and first hit with displayed prices suprised me. Combination insulated shutter with fly screen, automatic operation, coming in at less than half the price of pure fly screens I've looked at before. Feel like I've misunderstood or misremembered something.

[SteamyTea]

23 minutes ago, saveasteading said:

I can vouch for how effective these are in Mediterranean weather, keeping sun out in summer and heat in, in winter. 

Well the sun out is because the windows are small, the winter heat leaking out is because they are usually single glazed.

I don't know what it is about the British and the fixation with large windows.

[-rick-]

18 minutes ago, SteamyTea said:

Well the sun out is because the windows are small, the winter heat leaking out is because they are usually single glazed.

I don't know what it is about the British and the fixation with large windows.

 

Now show a modern equivalent mediteranian design. It will have large windows too (though also plenty of shading/overhangs most likely).

 

Old houses has small windows because glass couldn't be manufactured in large sizes. Once large glazing panels became viable people everywhere wanted to use it with varying levels of solar gain mitigation, from brute force carbon intensive mechanical forms to passive approaches.

[SteamyTea]

11 minutes ago, -rick- said:

Now show a modern equivalent mediteranian design. It will have large windows too (though also plenty of shading/overhangs most likely).

Like this one