Heat Loss in 1960's detached house

[LLL]

Hi everyone,

 

I live in a two-storey detached house built around the 1960s. It has traditional double-brick cavity wall construction and a crawl space under the ground floor, approximately 70–80 cm high and accessible. In winter, the house feels cold, and even when the heating is on, I feel that the warmth does not stay in the room for long. The heating bills are especially high during colder months. I’ve also noticed that during winter, there is significant condensation on the inside of windows, even though they are modern double-glazed units.

 

Here’s what I know and have already done:

 

The loft is fully insulated with mineral wool insulation.

All windows are modern double-glazed, but slight draughts can still be felt in very cold weather.

There is an original air vents / air brick on the wall in each room, which I’m considering blocking, as the property no longer uses fireplaces.

I’ve installed radiator reflective foil panels behind radiators located on external walls.

The cavity between the double-brick walls is not empty.

 

Given all this, I am trying to understand: Where is the majority of heat loss most likely happening in this type of house?

Is it mainly:

through the loft/roof,

via the suspended timber ground floor into the crawl space,

through the walls, or

through windows and doors (there are many!)?

 

I am considering insulating the ground floor from below by installing mineral wool insulation between the joists in the crawl space, supported by breathable netting. This might be some low-cost solution I can do myself, I believe.

Is this a practical and worthwhile solution in terms of heat retention and cost-saving? Or would the benefit be relatively limited compared to other improvements?

 

Thanks

[JohnMo]

23 minutes ago, LLL said:

The loft is fully insulated with mineral wool insulation.

But how deep?

23 minutes ago, LLL said:

All windows are modern double-glazed, but slight draughts can still be felt in very cold weather.

Replace seals, either replace with new seals from manufacturer or replacements from Screwfix etc

 

23 minutes ago, LLL said:

There is an original air vents / air brick on the wall in each room, which I’m considering blocking, as the property no longer uses fireplaces.

Don't you will cause way more issues with damp

24 minutes ago, LLL said:

 

Given all this, I am trying to understand: Where is the majority of heat loss most likely happening in this type of house?

Good guess will be drafts, you really need to understand where they come from and fix them, most is more time than cost. Draw curtains at night.

 

Also how do you operate your heating system, tell us time schedules, room thermostats or TRV - as much info as you can.  At lot of uncomfort comes from the way people operate the heating.

 

What boiler do you have system (with cylinder) or combi (no cylinder)?

[LLL]

6 minutes ago, JohnMo said:

But how deep?

Replace seals, either replace with new seals from manufacturer or replacements from Screwfix etc

 

Don't you will cause way more issues with damp

Good guess will be drafts, you really need to understand where they come from and fix them, most is more time than cost. Draw curtains at night.

 

Also how do you operate your heating system, tell us time schedules, room thermostats or TRV - as much info as you can.  At lot of uncomfort comes from the way people operate the heating.

 

What boiler do you have system (with cylinder) or combi (no cylinder)?

Thanks a lot! The fibreglass insulation is quite thick, I think it should be around 15-20cm. I'll have a look at the window seals, but since the windows are relatively new (6-8 years), how can I know whether I should change them or not? Is the condensation caused by the seal and a sign to change? There are too many windows and doors could cause drafts, any way to measure? and how about the walls? I have the Worcester combi boiler and the room temp is set between 17-19 degrees, depending on the time, most of the time I just put it on, only switching it off for a few hours in the night. Do you see it will be more energy efficient if i keep it on at a fixed temperature? This week until Friday, from the HIVE app, it shows the heating is on for 62 hours (I live in the north, so the temperature is lower). 

[-rick-]

22 minutes ago, JohnMo said:

Replace seals, either replace with new seals from manufacturer or replacements from Screwfix etc

 

Before doing this, confirm whether the draft is coming from the seals or from around the edge of the frame. Sounds more likely that the installers didn't seal around the frame too well (or it failed).

[JohnMo]

1 minute ago, LLL said:

how can I know whether I should change them or not?

Do they leak? if so maybe need to be changed

 

2 minutes ago, LLL said:

Is the condensation caused by the seal and a sign to change?

Where is the condensation - if on the glass, it would say your rooms are very cold or the ventilation isn't correct, photos help. Do your windows have trickle vents are they open of closed?

 

6 minutes ago, LLL said:

I have the Worcester combi boiler and the room temp is set between 17-19 degrees, depending on the time, most of the time I just put it on, only switching it off for a few hours in the night. Do you see it will be more energy efficient if i keep it on at a fixed temperature? This week until Friday, from the HIVE app, it shows the heating is on for 62 hours (I live in the north, so the temperature is lower). 

You say room temp, is that a single room or all rooms?

 

3 minutes ago, LLL said:

There are too many windows and doors could cause drafts, any way to measure?

A thermal camera, make the job quick, a candle flickering if held near a source of draft is a low cost options

[LLL]

6 minutes ago, -rick- said:

 

Before doing this, confirm whether the draft is coming from the seals or from around the edge of the frame. Sounds more likely that the installers didn't seal around the frame too well (or it failed).

thanks, i will check tonight when i am back 

[LLL]

5 minutes ago, JohnMo said:

Do they leak? if so maybe need to be changed

 

Where is the condensation - if on the glass, it would say your rooms are very cold or the ventilation isn't correct, photos help. Do your windows have trickle vents are they open of closed?

 

You say room temp, is that a single room or all rooms?

 

A thermal camera, make the job quick, a candle flickering if held near a source of draft is a low cost options

Condensation is on the glass, typically at the bottom half of the glass - I have no pictures today, but I can do it in some cold days. These days are warmer, with no condensation. Yes, there is a trickle vent on the top, I typically make it open during the summer time but off in winter to reduce the draft. The thermometre is set for the whole house; I put it in one of the bedrooms, there is no separate control for each room, unfortunately. 

[JohnMo]

10 minutes ago, LLL said:

no separate control for each room, unfortunately. 

To be quite frank, that's good. Lots of zone control can result in boiler running for very short cycles, bad for boiler life and has increased gas consumption.

 

I would start a new thread asking how best to insulate the floor from below. Because you want to stop heat being leached away, but also make draft free.

[JamesPa]

 

21 minutes ago, LLL said:

Condensation is on the glass, typically at the bottom half of the glass - I have no pictures today, but I can do it in some cold days. These days are warmer, with no condensation. Yes, there is a trickle vent on the top,

FWIW I suffered from this in some rooms.  Double glazing UPVC from the 80s. 

 

I replaced the sealed units (some of which may have 'gone' I think) with low e argon filled.  Now get condensation in bottom 2cm only and only on very coldest days.  It also made a noticeable difference to the house comfort.  I dont have trickle vents.  

 

If you can borrow a thermal imaging camera that may give useful insights, particularly if you have cold bridges or failed cavity wall insulation neither of which you can find by simple inspection (but of course they may not be easy to fix either!)

Edited Friday at 11:23 by JamesPa

[LLL]

4 minutes ago, JohnMo said:

To be quite frank, that's good. Lots of zone control can result in boiler running for very short cycles, bad for boiler life and has increased gas consumption.

 

I would start a new thread asking how best to insulate the floor from below. Because you want to stop heat being leached away, but also make draft free.

Thanks a lot, I am new and very keen to learn. The questions you have asked show you are very experienced. But to add my knowledge, do I need to keep the temperature fixed the whole day to make it more energy efficient? Do we need to make the trickle open in the wintertime as well (I can feel a draft immediately if I open it up)? Also, let's assume I have solved the draft problem (I feel this is not very serious), the cavity wall and the crawl space, which will leak more energy in winter? If the cavity wall is the main issue, I won't bother to do the crawl space insulation. Thank you very much! 

[LLL]

Also, compare with the heat loss from the wall and floor, is the draft (even a small one) much more serious and should be treated first? 

[Redbeard]

2 hours ago, LLL said:

The fibreglass insulation is quite thick, I think it should be around 15-20cm

 

To comply with current regs it should be at least 27cm deep. 40 or even 50cm is not too much for me, as long as you can get access when necessary.

[Conor]

What's in the cavities? Have you checked? And as Redbeard says, you want 400mm in the loft. It's by far the easiest and most cost effective way to improve insulation in the house. 

 

A few have mentioned drafts, but if you have condensation issues, im not sure that's a big issue.

[LLL]

1 hour ago, Conor said:

What's in the cavities? Have you checked? And as Redbeard says, you want 400mm in the loft. It's by far the easiest and most cost effective way to improve insulation in the house. 

 

A few have mentioned drafts, but if you have condensation issues, im not sure that's a big issue.

there is nothing in the cavities. For the loft, i agree the thicker the better, but at the bottom (crawl space), there is nothing below, is it more efficient to add insulation there instead of the loft? 

[SteamyTea]

TL:DR the replies.

It is worth doing a heat loss calculation on your house, then you may be able to target the areas that can be improved.

My guess is the suspended floor (it is a large area) and general air leakage are your main problems.

Double glazing, in isolation, does not cause condensation, it is caused by the interaction of humidity and temperature, you can get condensation at 40°C.

[marshian]

I've got a similar suspended timber floor with a 2 to 3 ft crawl space under it 

 

The void is ventilated with an air brick every 5 bricks so has a lot of air movement in winter

 

I've insulated between the Joists with 75mm PIR held up with blocks screwed to the joists (I know it looks like I could have used thicker but the picture below was the extending part of the house with much deeper joists - the rest of the house they are just 5 inch joists

 

It is without a doubt one of the best things I have done to improve the house 

 

However as a DIY task it sucked and took me several months to get this 

 

 

Cut to individual size (none of the joists are the same spacing or even parallel) and then moved to under the floor via 2 strategic hatches to limit the level of crawling around.

 

Absolutely awful job but the results have been brilliant.

 

I did have to install a PIV unit to take care of the ventilation strategy as a result of the insulation and drop in drafts the humidity level in the house sky rocketted but the PIV got it quickly under control.

[SteamyTea]

7 minutes ago, marshian said:

drop in drafts the humidity level in the house sky rocketted

Was that really caused by the reduction in uncontrolled ventillation or by an increase in internal temperature dry the structure out.  Have you tried checking the RH levels without the PIV switched on recently?

[marshian]

1 minute ago, SteamyTea said:

Was that really caused by the reduction in uncontrolled ventillation or by an increase in internal temperature dry the structure out.  Have you tried checking the RH levels without the PIV switched on recently?

 

I did the insulation install across spring and summer - the RH levels spiked as a result of occupants - the "uncontrolled" ventilation had been very effective in managing RH levels (At a cost in the heating seasons) 

 

If I turn the PIV off for a few days I pretty much see a steady increase in humidity over that period

 

It costs very little to run (it is run on a schedule not 24/7)

 

Real clue to the uncontrolled ventilation was in the carpet edges - cream carpet was black for an inch at the skirting edge...............

[LLL]

15 hours ago, marshian said:

I've got a similar suspended timber floor with a 2 to 3 ft crawl space under it 

 

The void is ventilated with an air brick every 5 bricks so has a lot of air movement in winter

 

I've insulated between the Joists with 75mm PIR held up with blocks screwed to the joists (I know it looks like I could have used thicker but the picture below was the extending part of the house with much deeper joists - the rest of the house they are just 5 inch joists

 

It is without a doubt one of the best things I have done to improve the house 

 

However as a DIY task it sucked and took me several months to get this 

 

 

Cut to individual size (none of the joists are the same spacing or even parallel) and then moved to under the floor via 2 strategic hatches to limit the level of crawling around.

 

Absolutely awful job but the results have been brilliant.

 

I did have to install a PIV unit to take care of the ventilation strategy as a result of the insulation and drop in drafts the humidity level in the house sky rocketted but the PIV got it quickly under control.

Thanks, compared with fiberglass, I am sure PIR is more tidy and easy to install. Do you leave a gap with the floor on the top to avoid moisture and potential mold? 

[marshian]

1 minute ago, LLL said:

Thanks, compared with fiberglass, I am sure PIR is more tidy and easy to install. Do you leave a gap with the floor on the top to avoid moisture and potential mold? 

 

No - it's pressed up against the underside of the chipboard floor - I had to re-do a bit of plumbing recently - so removed one section - no signs of any mold.

 

I have 3 ground floor surfaces in the house

 

Kitchen and Utility - 18mm Chipboard - 6mm Ply over boarding, Ceramic Tiles

Front Hall, Hallway, Toilet and Dining Room - 18mm Chipboard - 18mm Oak

Lounge - 18mm Chipboard - 6mm Ply over boarding and 20mm Oak 

[marshian]

Some discussion here
 

 

[marshian]

And here

 

 

 

[andeebee]

My 1960's dormer bungalow is also incredibly cold in the winter which is worse when the wind is blowing

Having recently removed the skirting in all the ground floor rooms, I found gaps you could fit your hand in, straight into the ventilated sub floor

The sub floor timbers were in perfect condition! 

I would check your rooms for air leakage points, as I imagine, like mine , some of your heated air is being drawn through the house and into the sub floor

Beyond that, but more intrusive, is insulating below the floorboards as others have mentioned

 

[Andehh]

I'd be using the semi rigid rock wool batters between the joists. Rigid enough could you push them between the joists and they should hold, until you screw some wood in, but flexible enough to take up the varying sizes of the joist spacing. 

[Onoff]

You would be amazed / shocked at the shoddy installs by "double glazing" fitters. A lot of the surveyors would under measure the gap so the install flew in. No chasing out etc. Ours got put in with damn great perimeter gaps that weren't foamed or expanding taped. They simply super glued trim over the gap and siliconed. Gradually redoing mine. Where the window is in situ I use Illbrück FM330 expanding foam. 

 

Trim removed and gap visible:

 

 

Finger size gaps:

 

 

Note no cavity closer either:

 

 

Lots of little things you can do and it all adds up. 

Edited 6 hours ago by Onoff