Help! : Possible Insulation Issues?

[rkinsella]

Hi folks,

We renovated our house in 2018 - 2019.

We put a lot of money into internal insulation - internally insulating the walls, the floor and ceilings.
We installed ultra low-U value windows throughout.
We installed a Thermia Atec Air 2 Water Heat Pump, along with underfloor heating etc.

You get the idea - bringing the house from the Irish E1 energy rating to an A3.
So on paper, I should be able to heat the house with a couple of candles

But it is still a modest house - 1350 sq feet only.
And it is proving expensive to heat, and appears to have little resilience to changes in outdoor temperature despite the insulation.

The purple bars below are the house's energy usage in kWh (left axis), and the red line is the outdoor temperature (right axis).
The temperature between the 16th and the 19th of January 2023 dropped just below zero, and our daily energy usage spikes to 45+ kWh per day.

We see the same pattern in December of 2022, with the temperature dropping into the deep minuses between the 7th and 17th of December.
Energy usage during this period is in excess of 50 kWh per day, and spikes to greater than 70 kWh on the 9th of December.

So all this is pretty costly at the current rate of €0.40 per kWh (thanks Mr Putin), you can imagine what my energy bills are like.

Is this lack of resilience simply due to the heat pump having to work harder because of lower temperatures?
Or does it point to a heat loss problem - how can I tell?

What are other people's experiences with heat pumps during cold weather - I expected more resilience to temperature changes.

 

[robinbanks]

Where is the thermostat located? What kind of insulation and how thick? What is the wall, floor and ceiling buildup? What did you do about air tightness? How warm do you keep your house? What flow temps have you set on your HP? How often do you ask it to produce a tank of hot water, to what temperature and how big? Has this pattern always exhibited and you've not noticed because energy was cheap or has there been a change recently? If you don't run the heating, but are active in the house, what temperature does the house sit at relative to the world?

 

[rkinsella]

Where is the thermostat located?

There are 4 in total - master bedroom, kids bedroom, guest bedroom and living area.
These control zone isolation valves, they are not wired directly into the heat pump.

What kind of insulation and how thick?

Kingspan 70mm cavity wall insulation throughout

What is the wall, floor and ceiling buildup?

Similar thickness in the floor as I recall. The ceiling was > 100mm as the roof insulation is in two layers, one overlaying the other in a latticed effect to cover the timbers.

What did you do about air tightness?

Nothing

How warm do you keep your house?

20C

What flow temps have you set on your HP?

I don't know what flow temps are. Here is a snapshot of the current temps.

Temperatures
Outdoor : 18°C
Indoor : Not installed
Supply line : 27°C
Tap water (top) : 50°C
System supply line : 27°C
Desired system supply line : 0°C

Is it fishy that Desired system supply line is 0°C?

How often do you ask it to produce a tank of hot water, to what temperature and how big?

We use a feature called hot water block, so that hotwater is only generated at certain times of the day.
50°C

Has this pattern always exhibited and you've not noticed because energy was cheap or has there been a change recently?

No change in the pattern - it has been expensive since day one.

If you don't run the heating, but are active in the house, what temperature does the house sit at relative to the world?

Good question - I haven't done an empirical analysis.
However the heatblock does come on during the working day, while I am working from home.

Inside temperatures generally stays above the outdoor temperatures. If it is 10C outside, it will be 15C inside without any heating.
Once I notice this, I generally light the wood burner - so it might go lower still given time.

 

[Mike13]

It has been noticed that Kingspan does have the headline figure of 0.022, but over time as the propane diffuses out it slowly changes to ~0.034 or so, also the thermal mass is too low so the "decrement delay" figure does not improve. It is quite silly that they keep finding that the running costs do not match the theory, and the building trade manufacturers do have a lot more work to do. A big thing is actually controlling the air leakage. An interesting sideline on that is a true "breathing wall" that was made in a university program test house with an actual negative U value, it needed a decent heat recovery unit in the exhaust to prevent the heat loss from costing too much.

 

[rkinsella]

It has been noticed that Kingspan does have the headline figure of 0.022, but over time as the propane diffuses out it slowly changes to ~0.034 or so, also the thermal mass is too low so the "decrement delay" figure does not improve. It is quite silly that they keep finding that the running costs do not match the theory, and the building trade manufacturers do have a lot more work to do.

Well we have had the issues since day one, so it unlikely that core issue is one of degradation overtime.

A big thing is actually controlling the air leakage. An interesting sideline on that is a true "breathing wall" that was made in a university program test house with an actual negative U value, it needed a decent heat recovery unit in the exhaust to prevent the heat loss from costing too much.

I was thinking about buying a thermal camera.
Should I be thinking about an air tightness test instead?

 

[Mike13]

Hi,

Home

The Passivhaus Trust, UK, adoption of the Passivhaus standard and methodology. leading international low energy, design standard. eco buildings, reducing energy use and carbon emissions. high standards of comfort and building health. Fabric First

www.passivhaustrust.org.uk

GreenSpec: Decrement Delay / Factor in the Building Envelope Fabric

Decrement delay is an important factor in building design. 

By controlling decrement delay it's possible to control and prevent the overheating of the building

www.greenspec.co.uk

these two will guide you to the next steps. the chances are that you house will be seriously leaky as far as air flow is concerned. I had endless problems with the builder of my extension just not understanding the issue. So you spend 500 euro and find you have a leaky house? what would you do next? Some things will be simple, others harder to get at.

The bottom line is that there are a lot of details to consider that make a house work as expected.

 

[robinbanks]

Insulation was probably fairly good for the time but it's a bit lacking now.. Shame that 70mm went in the floor, given that that's the heat emitter- making the floor insulation thicker would have been ideal, though it's a bit hard to do anything about it now..

For a long time the UK air tightness regs have been sorely lacking. The insulation requirements are getting to the point where they're beyond what a passivhaus requires but still we let builders get away with building leaky houses; a 10x10x3 metre bungalow as a passivhaus is allowed to lose 180 cubic metres of air an hour (0.6 of its volume of 300 cube). The same house under UK regs is allowed to lose 3200 cubes an hour (10x its envelope area of 320sqm). This is going to halve in 2025, but compared to a standard that lets buildings do away with heating systems we're letting builders get away with very poor work. It's no good lowering U value targets to the point where 300mm of kingspan is in every loft, if we permit gaps underneath it to the extent that all the house warm air can just blow away..

I do think an air tightness test would be quite interesting to do, and a thermal imaging camera would probably be helpful too - FLIR do ones that clip onto a smartphone, or they can be hired.. A cool night, heating having been on all day and some positive input pressure (can be as unsophisticated as an old car radiator fan in a piece of wood, mounted in an open door or window) to drive warm air out of the house and heat leaking parts of the fabric as it goes, or apply negative pressure, drawing cool air in and cooling parts of the fabric

 

[rkinsella]

Insulation was probably fairly good for the time but it's a bit lacking now.. Shame that 70mm went in the floor, given that that's the heat emitter- making the floor insulation thicker would have been ideal, though it's a bit hard to do anything about it now..

At the time it was a compromise between how much space we wanted to lose from the room, and the volume of insulation. We felt that 70mm was a good compromise, we could have done more.

For a long time the UK air tightness regs have been sorely lacking. The insulation requirements are getting to the point where they're beyond what a passivhaus requires but still we let builders get away with building leaky houses; a 10x10x3 metre bungalow as a passivhaus is allowed to lose 180 cubic metres of air an hour (0.6 of its volume of 300 cube). The same house under UK regs is allowed to lose 3200 cubes an hour (10x its envelope area of 320sqm). This is going to halve in 2025, but compared to a standard that lets buildings do away with heating systems we're letting builders get away with very poor work. It's no good lowering U value targets to the point where 300mm of kingspan is in every loft, if we permit gaps underneath it to the extent that all the house warm air can just blow away..

There are very generous supports available here to renovate houses, on paper the government contributes very significant sums to the work if
you are willing to build the house to passivhaus-like standards. They will even do all the work for nothing, if your income is below a threshold. In practice we found the companies who would take on this work quoted us some pretty crazy sums.

In the end, we applied for the smaller individual grants to install the heatpump and insulation, but very little else - and saved ourselves about €100k in the process. In retrospect, the air tightness test at the end of the build would probably have been a good idea.

I do think an air tightness test would be quite interesting to do, and a thermal imaging camera would probably be helpful too - FLIR do ones that clip onto a smartphone, or they can be hired.

I think so, too - good advice.

A cool night, heating having been on all day and some positive input pressure (can be as unsophisticated as an old car radiator fan in a piece of wood, mounted in an open door or window) to drive warm air out of the house and heat leaking parts of the fabric as it goes, or apply negative pressure, drawing cool air in and cooling parts of the fabric

 

[rkinsella]

Hi,

Home

The Passivhaus Trust, UK, adoption of the Passivhaus standard and methodology. leading international low energy, design standard. eco buildings, reducing energy use and carbon emissions. high standards of comfort and building health. Fabric First

www.passivhaustrust.org.uk

GreenSpec: Decrement Delay / Factor in the Building Envelope Fabric

Decrement delay is an important factor in building design. 

By controlling decrement delay it's possible to control and prevent the overheating of the building

www.greenspec.co.uk

these two will guide you to the next steps. the chances are that you house will be seriously leaky as far as air flow is concerned. I had endless problems with the builder of my extension just not understanding the issue. So you spend 500 euro and find you have a leaky house? what would you do next? Some things will be simple, others harder to get at.

I got the loan of a CAT mobile phone with an infrared camera about a year ago, and I noticed a few things.

I got the impression that the wall sockets on external walls are leaking a lot of cold air into the room. The socket's box / wall plate is secured to the original exterior masonry wall, with very long screws to attach the socket faces on the pasterboard insulation. So there is a deep gap between the socket face and wall plate, surrounded by the internal insulation.

I imagine its the same for the electrical fittings mounted on the outer walls. I had thought I might stuff some insulation in the a gap - but I was worried about it being safe?

I also noticed the corners where the ceiling meets the exterior wall, showed up as cold spots. So I am guessing the builder wasn't too careful about ensuring airtightness there - anything I can do about this.

I might buy a flir and spent more time on this.

The bottom line is that there are a lot of details to consider that make a house work as expected.

 

[Mike13]

Yes, I also had the builder trying to deliver sockets with no insulation behind them! seems to be a common theme. It made a difference to fix that. If there is enough slack in the wires you can gently pull out the backbox and then insulate behind. If the wires are a bit short that wont be possible, so would have to be done with a spray foam of whatever is suitable locally.

 

[rkinsella]

Out of interest, what did you use to insulate behind the back box?

 

[Mike13]

I used Kingspan cut to size and spray foam to fill the inevitable gaps

 

[rkinsella]

Good idea. I'll get a sheet of 40mm kingspan from the local builders yard.

 

[robinbanks]

So I am guessing the builder wasn't too careful about ensuring airtightness there - anything I can do about this.

There is always something that can be done, it just depends how much of a mess you want to make. Drilling a hole and poking a camera (usb cameras for inspecting drains, on a long wire for example) into awkward spots can be a low/invasion way of getting a look at a problem. Cutting out a section of plasterboard using an oscillating multi tool leaves a neat cut that can be fairly easily patched in afterwards..

Do the blower test and see if you have an air leak problem - if you do, look to remedy. If you don't, you likely have a "world air is getting to the warm side of the insulation" problem

 

[Mike13]

There is always "seconds and Co" on fleabay and direct, sometimes they do smaller bundles.