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 39 minutes ago 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?