Optimizing window insulation- curtains/blinds

An_Toirpin

I am looking at how to maximize window insulation. It seems curtains are a very common place where houses underperform, due to thin material or poor hanging. It is surprising how little attention is paid to details in such a cool climate.


I am keen to avoid this but I am having difficulty finding the best models out there. Lined blackout curtains seem to be a good candidate but actual stats seem hard to come by. There are some companies that make cellular blinds which are supposed to be have excellent R values but it is not clear how these compare to lined blackout curtains. Blinds don't overhang or touch the floor which might put them at a disadvantage?

selfbuild17

I would imagine that the impact on window insulation provided by blinds/curtains would be very limited. No matter how much an overhang you have, air will be continuously circulating around the curtains.

Lumen

The performance of curtains and blinds is a matter of convection, not conduction, and so R values are meaningless.

A properly constructed house should not rely on window coverings for energy efficiency.

Gumbo

An_Toirpin wrote: »

I am looking at how to maximize window insulation. It seems curtains are a very common place where houses underperform, due to thin material or poor hanging. It is surprising how little attention is paid to details in such a cool climate.


I am keen to avoid this but I am having difficulty finding the best models out there. Lined blackout curtains seem to be a good candidate but actual stats seem hard to come by. There are some companies that make cellular blinds which are supposed to be have excellent R values but it is not clear how these compare to lined blackout curtains. Blinds don't overhang or touch the floor which might put them at a disadvantage?

Most people have curtains because they like them or want to draw them for privacy. Insulation properties would be way down in the mindset of the typical home owner I would imagine.

Dudda

The only window dressing I've seen used successfully to improve window insulation was insulated window shutters. 40mm of PIR insulation between two layers of veneered ply in a timber frame. They had rubber seals to the perimeter to make them airtight.

BryanF

‘Optimizing’ window insulation

I’ve recently installed 3g 0.8w/m2k door and window

Very happy with the window ‘insulation’

Metric Tensor

To be fair lads - in the days of sh!tty single glazed half rotten timber windows a set of heavy fabric curtains made a lot of difference to the heat retention in old houses. As pointed out - probably by preventing convection more than radiation.

It's before my time but my great grandmother had separate summer and winter curtains for that reason.

In the days of triple glazed windows sealed air tight to the wall opes they may not have much benefit but there are people still living in old or heritage buildings who, for whatever reason, can't upgrade crappy windows.

As a more modern example I know a circa 30 year old house with thin double glazed windows in non thermally broken aluminium frames and you can tell the difference between rooms with the curtains open and closed. (These are heavy, fleece lined curtains.)

So to the OP. It won't help in a new house but it could in an old house - try and install them in a way that would stop or block draughts through poorly installed frames. In terms of heat retention I suppose it's a bit like shopping for a tog value with a duvet!

An_Toirpin

Lumen wrote: »

The performance of curtains and blinds is a matter of convection, not conduction, and so R values are meaningless.

A properly constructed house should not rely on window coverings for energy efficiency.

Thanks for the advice. The house is a 2017 build bought off the plans but the windows aren't great. I have curtains in some of the rooms and they seem to have made a big impact so I wouldn't agree at all with most of the comments. They may work only through convection but it's hardly going to be consistent throughout different types of window dressings. So the question remains unanswered.

By the way not sure triple glaze are anything near the norm yet.

An_Toirpin

kceire wrote: »

Most people have curtains because they like them or want to draw them for privacy. Insulation properties would be way down in the mindset of the typical home owner I would imagine.

I agree, but it seems a oversight.

listermint

Curtains will 100% assist in retaining heat in a room without a doubt. Had an ex who's mother used to have them throughout the rented property including front door and without them the place was Baltic.


You don't however need to be concerned with r value. Buy some 'heavy' curtains. Its a blanket term so to speak but if you can imagine heavy curtains then that's what I'm on about.

lawred2

An_Toirpin wrote: »

Thanks for the advice. The house is a 2017 build bought off the plans but the windows aren't great. I have curtains in some of the rooms and they seem to have made a big impact so I wouldn't agree at all with most of the comments. They may work only through convection but it's hardly going to be consistent throughout different types of window dressings. So the question remains unanswered.

By the way not sure triple glaze are anything near the norm yet.

A 2017 build should not be compromised by poor windows..

What's the issue with them?

An_Toirpin

lawred2 wrote: »

A 2017 build should not be compromised by poor windows..

What's the issue with them?

I agree that it should nt but they are very cold. Irish building controls are awful. It is A2, and supposedly had it's own BER conducted. However considering that when we first moved in that it took hours of constant heating to make the house 21c and would rapidly drop once off, I have serious concerns about the integrity/ competence of BER assessors. Im digressing but I could see plenty of examples of sloppines. Turn off the heating and the house could go to 6c.

lawred2

An_Toirpin wrote: »

I agree that it should nt but they are very cold. Irish building controls are awful. It is A2, and supposedly had it's own BER conducted. However considering that when we first moved in that it took hours of constant heating to make the house 21c and would rapidly drop once off, I have serious concerns about the integrity/ competence of BER assessors. Im digressing but I could see plenty of examples of sloppines. Turn off the heating and the house could go to 6c.

That doesn't sound good at all.

Ours is A2. Recently left the house for four days over Christmas. Put the heating in Holiday mode (off effectively) and when we got back the house was only three degrees cooler than when we left.

Roen

If you want to go the big money route bloc blinds are great at keeping heat in/out and form a near light tight seal about the whole window.
That said I think curtains and blinds are the least of your worries and should be one of your past ports of call.

We have them in one room only for the baby and they work great.

listermint

The BER system is an incredibly flawed expensive box ticking exercise. It quite literally is a check list and a mathematical calculation with zero concern for quality installation of products.

You could have a house with all the best materials that were very poorly installed and still achieve a nice solid A2


How you can trust that is beyond me.

Gumbo

An_Toirpin wrote: »

I agree that it should nt but they are very cold. Irish building controls are awful. It is A2, and supposedly had it's own BER conducted. However considering that when we first moved in that it took hours of constant heating to make the house 21c and would rapidly drop once off, I have serious concerns about the integrity/ competence of BER assessors. Im digressing but I could see plenty of examples of sloppines. Turn off the heating and the house could go to 6c.

A 2017 house should not need curtains in my
Opinion. Holding control/regulations in Ireland are amongst the highest standard in the worlds. Everyday on these very forums people moan about them
Being too strict and we should be relaxing them during the housing crisis (entitlement crisis).

At A2 rating, the air tightness of the dwelling would of having to be tested and imputed into the DEAP calculation so in theory the BER should have a relatively close relationship to your dwelling.

Another note, 21 degrees is quite high by Irish standards. 16-20 is the norm and it requires a lot of energy to heat a home to 21 degrees.

An_Toirpin

kceire wrote: »

A 2017 house should not need curtains in my
Opinion. Holding control/regulations in Ireland are amongst the highest standard in the worlds. Everyday on these very forums people moan about them
Being too strict and we should be relaxing them during the housing crisis (entitlement crisis).

At A2 rating, the air tightness of the dwelling would of having to be tested and imputed into the DEAP calculation so in theory the BER should have a relatively close relationship to your dwelling.

Another note, 21 degrees is quite high by Irish standards. 16-20 is the norm and it requires a lot of energy to heat a home to 21 degrees.

There is an airtightness measurement in the XML but I don't know how to interpret it. At first the house would take heating in both zones to be on for four hours or so to get to 21c. I started caulking gaps to improve the situation but before this the house never went beyond 22c all winter long. A few times I really tried to get it warmer but I couldnt. Heating to 21c takes a lot of energy but the house has gas heating which produces huge amounts of energy.


I really don't know how warm A2 houses should be but double glazed windows are inevitably going to be cold spots, so I would have thought curtains would help even very warm houses, no?



Thanks all for the comments.

Dudda

An_Toirpin wrote: »

There is an airtightness measurement in the XML but I don't know how to interpret it. At first the house would take heating in both zones to be on for four hours or so to get to 21c. I started caulking gaps to improve the situation but before this the house never went beyond 22c all winter long. A few times I really tried to get it warmer but I couldnt. Heating to 21c takes a lot of energy but the house has gas heating which produces huge amounts of energy.


I really don't know how warm A2 houses should be but double glazed windows are inevitably going to be cold spots, so I would have thought curtains would help even very warm houses, no?



Thanks all for the comments.

Your house has a much bigger problem if you've gas heating, an A2 rating and are having to consider curtain to warm up the place. When I replied first to this thread I presumed it was an old Georgian property with historic single glazed windows or similar.

Would you consider posting the detailed results of your BER cert with the front page with your details and any other bits that could identify your or the property removed?

Idbatterim

An entitlement crisis? Is this after hours or the journal?!

An_Toirpin

Dudda wrote: »

Your house has a much bigger problem if you've gas heating, an A2 rating and are having to consider curtain to warm up the place. When I replied first to this thread I presumed it was an old Georgian property with historic single glazed windows or similar.

Would you consider posting the detailed results of your BER cert with the front page with your details and any other bits that could identify your or the property removed?

Delighted too. Is this information enough?

ber.jpg

listermint

kceire wrote: »

A 2017 house should not need curtains in my
Opinion. Holding control/regulations in Ireland are amongst the highest standard in the worlds. Everyday on these very forums people moan about them
Being too strict and we should be relaxing them during the housing crisis (entitlement crisis).

At A2 rating, the air tightness of the dwelling would of having to be tested and imputed into the DEAP calculation so in theory the BER should have a relatively close relationship to your dwelling.

Another note, 21 degrees is quite high by Irish standards. 16-20 is the norm and it requires a lot of energy to heat a home to 21 degrees.

They don't test every house in an estate though for air tightness they test one and then check list he rest for standard ber.

Claiming we have tight regulations is all fine but we have incredibly lax enforcement.

Metric Tensor

The OPs BER equates to an air-tightness of approx 4.7 ACH at 50 Pa.

This is pretty poor for a modern house. But should not be enough to stop the temp from rising above 21.

Technically TGD L says if the assessor used a value of less than 7 in the assessment the specific house should have been tested rather than relying on the value from another in the estate. Although I know this rule is not observed in many cases.

Metric Tensor

P.S. As if April(ish) ALL houses will require an air-tightness test. A subset will no longer be sufficient

Dudda

An_Toirpin wrote: »

Delighted too. Is this information enough?

ber.jpg

Thanks. The window sizes and losses aren't huge. Is not like you've giant walls of glass to take in views. The heating load isn't massive either and the gas boiler should easily handle it. Do you've any issues with hot water and is it under floor heating or radiators? I wonder if air is trapped, a mixing valve, pump or something like that isn't working properly.
With a radiator you can put your hand on it to check but with underfloor heating it can sometimes be hard to tell if it's not working at 100%.
I confused because of two things. It shouldn't take long to heat up with gas boiler and a fairly small heating load and second it should hold heat a lot better particular if underfloor as that gives heat out longer.

An_Toirpin

Metric Tensor wrote: »

P.S. As if April(ish) ALL houses will require an air-tightness test. A subset will no longer be sufficient

Metric Tensor wrote: »

The OPs BER equates to an air-tightness of approx 4.7 ACH at 50 Pa.

This is pretty poor for a modern house. But should not be enough to stop the temp from rising above 21.

What ACH value can one aspire to in a modern semi-D house with no airtighntess membrane and no fire place?

Dudda wrote: »

Thanks. The window sizes and losses aren't huge. Is not like you've giant walls of glass to take in views. The heating load isn't massive either and the gas boiler should easily handle it. Do you've any issues with hot water and is it under floor heating or radiators? I wonder if air is trapped, a mixing valve, pump or something like that isn't working properly.
With a radiator you can put your hand on it to check but with underfloor heating it can sometimes be hard to tell if it's not working at 100%.
I confused because of two things. It shouldn't take long to heat up with gas boiler and a fairly small heating load and second it should hold heat a lot better particular if underfloor as that gives heat out longer.

I will try this. I could see fibreglass was missing in a lot of the attic space and there was a lot of gaps in skirting. I have been working on this and it seems to have helped a lot.

Wartburg

Metric Tensor wrote: »

The OPs BER equates to an air-tightness of approx 4.7 ACH at 50 Pa.

This is pretty poor for a modern house. But should not be enough to stop the temp from rising above 21.

Technically TGD L says if the assessor used a value of less than 7 in the assessment the specific house should have been tested rather than relying on the value from another in the estate. Although I know this rule is not observed in many cases.

I disagree regarding the air changes. The DEAP value is the air permeability at 50Pa differential pressure divided by 20. That leads to an air permeability of 4.7m³/hm² at 50Pa. The air change rate can be higher or lower. Probably not that much but definitely not exactly 4.7ACH. It´s (almost) impossible that the building volume has the same value like the building envelope.

Metric Tensor

Wartburg wrote: »

I disagree regarding the air changes. The DEAP value is the air permeability at 50Pa differential pressure divided by 20. That leads to an air permeability of 4.7m³/hm² at 50Pa. The air change rate can be higher or lower. Probably not that much but definitely not exactly 4.7ACH. It´s (almost) impossible that the building volume has the same value like the building envelope.

Apologies. You are totally correct.

I fall into the trap of treating the two as interchangeable - which of course they are not at all unless the volume of the house is at a coincidental value.

Wartburg

An_Toirpin wrote: »

What ACH value can one aspire to in a modern semi-D house with no airtighntess membrane and no fire place?

I tested a bungalow last year, where no membranes and air tight tapes have been installed when it was built in 2008. The test ended with an air change rate of 2.3 1/h and an air permeability of 2.06 m³/m2h at 50 Pa differential pressure. I even left the cooker hood and one wall vent open, because I wanted to see the performance under real conditions by living in this house myself at this time.

The top ceiling and the sealing around the windows aren´t the biggest issues for the air tightness in a semi D. The most air infiltrates through your ceiling between the two floor levels, because the most houses in recent years have nice details inside this area as shown in the attached photo.

4068ac1elhodqr

Installed one of those €2 bargain bin type of insulation sheets on a very large awkward tall (DG) window at the back hall.
Creates an instant 20mm pocket of air to prevent heat radiation loss.

It's not pretty and not 100% (maybe 95-7%) performance wise, but does makes a huge difference to heat loss.
Don't have to bother with curtains, and thus no issues with loss of daylight.

Wartburg

Metric Tensor wrote: »

Apologies. You are totally correct.

I fall into the trap of treating the two as interchangeable - which of course they are not at all unless the volume of the house is at a coincidental value.

No need for apologies. The entire procedure of air changes and air permeability is confusing enough. I do not know where the SEAI has taken the wisdom of converting a value with m³/h²m into a value with 1/h just by dividing by 20. They might can make wine out of water as well ;-)

robp

Wartburg wrote: »

I tested a bungalow last year, where no membranes and air tight tapes have been installed when it was built in 2008. The test ended with an air change rate of 2.3 1/h and an air permeability of 2.06 m³/m2h at 50 Pa differential pressure. I even left the cooker hood and one wall vent open, because I wanted to see the performance under real conditions by living in this house myself at this time.

The top ceiling and the sealing around the windows aren´t the biggest issues for the air tightness in a semi D. The most air infiltrates through your ceiling between the two floor levels, because the most houses in recent years have nice details inside this area as shown in the attached photo.

Accessing and sealing those holes in the concrete certainly adds to my to list of DIY projects!

An_Toirpin

Wartburg wrote: »

I tested a bungalow last year, where no membranes and air tight tapes have been installed when it was built in 2008. The test ended with an air change rate of 2.3 1/h and an air permeability of 2.06 m³/m2h at 50 Pa differential pressure. I even left the cooker hood and one wall vent open, because I wanted to see the performance under real conditions by living in this house myself at this time.

The top ceiling and the sealing around the windows aren´t the biggest issues for the air tightness in a semi D. The most air infiltrates through your ceiling between the two floor levels, because the most houses in recent years have nice details inside this area as shown in the attached photo.

Fascinating to see that details. Would you seal all of those gaps with cement, electrical cables holes and all?

Wartburg

An_Toirpin wrote: »

Fascinating to see that details. Would you seal all of those gaps with cement, electrical cables holes and all?

All the gaps on the photo have been sealed with standard foam & taped with air tight tape afterwards. Also the block was covered with hard coat.
With the materials and technologies nowadays, I´m using air tight foam and air tight paint to get such details sorted.

an_fathach

Wartburg wrote: »

All the gaps on the photo have been sealed with standard foam & taped with air tight tape afterwards. Also the block was covered with hard coat.
With the materials and technologies nowadays, I´m using air tight foam and air tight paint to get such details sorted.

I was reading this old thread and I am interested in this detail a lot. I imagine in this house there is a drylining? When you seal these holes in the concrete wall is there any risk of any problems with moisture, because aren't you moving the airtightness and vapour layer back? I am asking as a real noob.

moldy_sea

BryanF wrote: »

‘Optimizing’ window insulation

I’ve recently installed 3g 0.8w/m2k door and window

Very happy with the window ‘insulation’

Could you share which brand you chose?