New build - cold bedroom

[joth]

Further to everything @AliG says, if the house air temp increases so quickly in 30min it means you must be running the heating at a fairly high flow temperature. Try turning the boiler flow temperature down (e.g. to 30 or so rather than 50 or more) and run it for longer.

This will both be cheaper (as a condensing boiler is more efficient this way) and also give a longer period for the walls and building fabric to warm up.

 

I assume you have TRVs through out all radiators, so you may need to tune these a bit to stop downstairs rooms overheating. Installing something like Tado smart thermostats can help a bit with these sorts of experiments and in confirming (based on its estimate model) as how much energy each room is sinking.

 

Ultimately you need to determine if its convection or conduction heat losses, and if it is through floors, walls, doors or windows, and there's a limit how much help you can get with that online vs doing the investigation in real life.

 

[Drellingore]

Apologies if you've already thought of this and tried it, but are there any differences in curtain configuration? I'm sure it won't be the root of your problem, but might help a little to stem the losses.

 

Our bedrooms (was a cheapo Fairview newbuild in 2012) lose warmth really quickly when the curtains are drawn, and even when they just hang down below the windowsill. Bunching them up onto the windowsills really makes a difference, even if that does lead to condensation on the windows.

[Littlebig]

4 hours ago, JohnMo said:

Not a good idea to block these ventilation paths, as they are there for ventilation.

 

When you say they replaced the trickle vents on the windows, what did they replace then with, like for like or something different?

I understand these gaps under the internal doors are somewhat standard to allow the air to circulate but I don’t try and reduce that air flow the heat loss will be even greater. I have a draught excluder which has reduced the air flow not completely blocked it, but didn’t have it last year and can’t say how beneficial it is yet.

The window fitter came to replace the handle on the window and I asked for few spare trickle vents as I broke one downstairs and replaced a total of 3 myself which were like for like.

[Littlebig]

3 hours ago, AliG said:

Thanks for the info posted.

 

As @JohnMo said normally you would not draught proof internal doors so that air can circulate. Also is the hall actually that much colder than the bedrooms?

 

Without an IR camera it is hard to tell if there is an issue in the walls. If there was an issue, once it is quite cold (like last night) the walls in the problem room would probably feel colder to the touch than in the other bedroom.

 

I would have though that the most likely place to lose heat is via cold air in the floor but this would probably impact both bedrooms equally.

 

TBH the temperature drop you mentioned last night is less concerning than what you mentioned at first. If you turned the heating off at 630pm and it got down to 3C outside then it would indeed cool down quite a bit in the bedroom. A well insulated self build might drop 1-2C over that period. Really in an average house I don't think you can expect to turn the heating off at 630pm and it still to be warm 12 hours later when it is 3C outside.

Your bedroom would have been warmer in the morning as you and your partner generate a lot more body heat than a baby.

 

Also you need to consider the construction of your house in how you run the heating. I assume that you have solid wet plastered walls if they are blockwork. When you turn on the heating, it will heat the air quickly as air holds a lot less heat than concrete. If you only had the heating on for half an hour the air would have likely heated up but not the walls. Then once you turn the heating off the walls will actually suck heat out of the air as their temperature equalises with the air. This would not happen so much in a timber frame house where the walls have less mass. If we were properly into winter and the heating had been on for a long period then the heat stored in the walls would actually help to keep the air temperature steadier, but when it first starts to get cold your house will take more heating to warm up the walls.

In all fairness the temp. drop was within an acceptable range considering the heating was only on for about 30mins, and yes totally agree our room will be warmer because of our body heat.

The only problem is that lets say temp. outside drops to -2-3C the nursery room drops to 16C (the case last year) which is fairly low and it does happen rather quick.
I can’t remember if I mentioned this here but both radiators in the bedrooms were replaced with bigger ones and this has significantly improved the time it takes to warm up as even when heating is turned off they keep warm for longer.

In the winter months we do keep the heating on for longer but at the moment the temp. outside is still fairly high and it doesn’t take too long to heat up as it is a small house.

[Littlebig]

3 hours ago, joth said:

Further to everything @AliG says, if the house air temp increases so quickly in 30min it means you must be running the heating at a fairly high flow temperature. Try turning the boiler flow temperature down (e.g. to 30 or so rather than 50 or more) and run it for longer.

This will both be cheaper (as a condensing boiler is more efficient this way) and also give a longer period for the walls and building fabric to warm up.

 

I assume you have TRVs through out all radiators, so you may need to tune these a bit to stop downstairs rooms overheating. Installing something like Tado smart thermostats can help a bit with these sorts of experiments and in confirming (based on its estimate model) as how much energy each room is sinking.

 

Ultimately you need to determine if its convection or conduction heat losses, and if it is through floors, walls, doors or windows, and there's a limit how much help you can get with that online vs doing the investigation in real life.

 

The boiler (LOGIC COMBI ESP1 30)  is set at the economy mark since the bedroom radiators were replaced. It’s just not that cold inside and/or outside to have to run the heating for long periods. We have TRV valves on all radiators except the two where we have the thermostats in the rooms (master bedroom & lounge).

Downstairs room is not overheating, just on a sunny day it gets warm from the sun and also due to the size of the lounge when we use the oven it gets warm as well so we only put the heating on downstairs mainly in the morning and is alright pretty much all day.

This is what I’m trying to determine where the heat loss is coming from and all I can think is the gap under doors, walls or the windows as I don’t think is the floor.

 

PS: I don’t know much about combi boilers (I’m electrical engineer and have knowledge on many electrical appliances 😂) but if you or anyone else can let me know what could be the best settings for it I’m more than happy to try it.

Edited November 4, 2022 by Littlebig

[Littlebig]

1 hour ago, Drellingore said:

Apologies if you've already thought of this and tried it, but are there any differences in curtain configuration? I'm sure it won't be the root of your problem, but might help a little to stem the losses.

 

Our bedrooms (was a cheapo Fairview newbuild in 2012) lose warmth really quickly when the curtains are drawn, and even when they just hang down below the windowsill. Bunching them up onto the windowsills really makes a difference, even if that does lead to condensation on the windows.

This is something we tried as well. When we first bought the curtains we thought we will get then cut to size to go just behind the radiators when drawn. Due to the fact that we bough them from Next it was cheaper to leave them in full length and when the heating is on we just bunch them up on the windowsill. In the nursery room though we changed them to match the light and chair colour and they are just long enough to fit behind the radiator when drawn. As a lot of these “improvements” were made towards the end of the winter or in the summer I will have to wait for some cold winter days and nights and see what has helped and what not.

[AliG]

Is the temperature dropping as much in the lounge overnight as the bedrooms? Has the lounge had the heating on for longer than half an hour to heat up the fabric of the room more? As you say the lounge and kitchen will have a lot of heat input from ovens, TVs etc over the day.

 

I am guessing that your house has 100mm of mineral wool in the cavity which is the bare minimum required to pass building regs. This gives a U-value of around 0.28 which is very poor today.

 

The maximum roof U-value in England is 0.18 and the maximum window U-value is 1.4

 

Assuming these numbers the room will lose around 75W an hour through the walls, 35W through the window and 30W through the ceiling with an outside temp of 3C. If for example the bathroom or hall are not heated then further heat would be lost to these areas. I assumed a room size of 3.5x2.5x2.4m and 1.5sq metres for the window. These will give a rough idea.

 

You can probably double the heat loss including ventilation losses, but this would be a guesstimate.

 

Thus the room will likely need around 2-300W of energy to keep a constant temperature during the night. I am assuming a 21C internal room temperature and 18C differential to calculate heat loss. The heat loss is directly proportional to the differential, so if the outside temperature is 12C as it has been during the day recently, then the heat loss halves versus 3C night time temperature in the last couple of days. The day also benefits from solar radiation and heat generated by activity in the house thus requires a lot less heat input.

 

Assuming that the room has a volume of 20m3, that is roughly 24kg of air. The energy required to increase the temperature of 24kg of air by 1C is roughly 24Kj. So to heat the room air by 3C requires 72Kj or only 20Wh of energy.

 

However, assuming 120mm of blockwork/plaster. The outside walls of the room weigh around 1500kg. The specific heating capacity of this would be around 1Kj per kg. Thus to heat the walls up by 3C would require around 4500Kj or 1260Wh.

 

I don't know what size of radiator you have in there but say it has a 3-400W output. It could easily warm the air by 3C in half an hour (20Wh required versus 150-200Wh of output), but you would need to run it for 3-4 hours for the walls to be up to the same temperature as the air. Once the walls are up to that temperature then you will only have to overcome the 200-300W heat loss, but initially you have a large deficit to make up.

 

Net net at 3C outside during the night, if the heating was on for 12 hours, I would expect it to be actually running for around 75% of the time. (Very dependant on the radiator size assumption). The size assumption just affects the time the radiator runs for, the amount of energy required to heat the room is the same it can just be provided faster by a lager radiator/higher flow temperature. Basically you cannot run the heating for half an hour and expect the temperature not to drop quickly on a cold night. If you ran the heating for 4-5 hours in the evening I would expect to see much less temperature drop as the walls would be up to temperature. Their relatively high heat capacity would lead to a more constant air temperature. Basically set the thermostat at 21C at 5pm and leave the heating on until 9 or 10. It would not run constantly, but it would run a lot of the time whilst the walls warm up. Then I would expect a much steadier temperature during the night. However, the poor insulation levels of the house mean that even then I would expect it to be somewhat colder by the morning as you have quite a lot of heat loss at 3C outside.

 

If the walls have not heated up and are materially colder than the air in the room, due to their dramatically larger heat capacity they will take energy from the air and cool the room down during the night.

 

[MikeGrahamT21]

99% sure you’ll have dot and dab plasterboards on your walls, and this is likely a big contributor to your issues, take a socket face plate off on a windy day, if it blows a gale, we’ll I’m sure you can imagine what’s happening behind there…

[Littlebig]

On 04/11/2022 at 20:18, AliG said:

Is the temperature dropping as much in the lounge overnight as the bedrooms? Has the lounge had the heating on for longer than half an hour to heat up the fabric of the room more? As you say the lounge and kitchen will have a lot of heat input from ovens, TVs etc over the day.

 

I am guessing that your house has 100mm of mineral wool in the cavity which is the bare minimum required to pass building regs. This gives a U-value of around 0.28 which is very poor today.

 

The maximum roof U-value in England is 0.18 and the maximum window U-value is 1.4

 

Assuming these numbers the room will lose around 75W an hour through the walls, 35W through the window and 30W through the ceiling with an outside temp of 3C. If for example the bathroom or hall are not heated then further heat would be lost to these areas. I assumed a room size of 3.5x2.5x2.4m and 1.5sq metres for the window. These will give a rough idea.

 

You can probably double the heat loss including ventilation losses, but this would be a guesstimate.

 

Thus the room will likely need around 2-300W of energy to keep a constant temperature during the night. I am assuming a 21C internal room temperature and 18C differential to calculate heat loss. The heat loss is directly proportional to the differential, so if the outside temperature is 12C as it has been during the day recently, then the heat loss halves versus 3C night time temperature in the last couple of days. The day also benefits from solar radiation and heat generated by activity in the house thus requires a lot less heat input.

 

Assuming that the room has a volume of 20m3, that is roughly 24kg of air. The energy required to increase the temperature of 24kg of air by 1C is roughly 24Kj. So to heat the room air by 3C requires 72Kj or only 20Wh of energy.

 

However, assuming 120mm of blockwork/plaster. The outside walls of the room weigh around 1500kg. The specific heating capacity of this would be around 1Kj per kg. Thus to heat the walls up by 3C would require around 4500Kj or 1260Wh.

 

I don't know what size of radiator you have in there but say it has a 3-400W output. It could easily warm the air by 3C in half an hour (20Wh required versus 150-200Wh of output), but you would need to run it for 3-4 hours for the walls to be up to the same temperature as the air. Once the walls are up to that temperature then you will only have to overcome the 200-300W heat loss, but initially you have a large deficit to make up.

 

Net net at 3C outside during the night, if the heating was on for 12 hours, I would expect it to be actually running for around 75% of the time. (Very dependant on the radiator size assumption). The size assumption just affects the time the radiator runs for, the amount of energy required to heat the room is the same it can just be provided faster by a lager radiator/higher flow temperature. Basically you cannot run the heating for half an hour and expect the temperature not to drop quickly on a cold night. If you ran the heating for 4-5 hours in the evening I would expect to see much less temperature drop as the walls would be up to temperature. Their relatively high heat capacity would lead to a more constant air temperature. Basically set the thermostat at 21C at 5pm and leave the heating on until 9 or 10. It would not run constantly, but it would run a lot of the time whilst the walls warm up. Then I would expect a much steadier temperature during the night. However, the poor insulation levels of the house mean that even then I would expect it to be somewhat colder by the morning as you have quite a lot of heat loss at 3C outside.

 

If the walls have not heated up and are materially colder than the air in the room, due to their dramatically larger heat capacity they will take energy from the air and cool the room down during the night.

 

Well your pretty much spot on in your calcs. I’m not convinced I have mineral wool insulation into the wall cavity, I think insulation has been blown in judging by what I’ve seen on the other house that they are building in the estate. We usually have the heating on in the winter (on cold days) on for few hours mainly on the night but I will try an have it on for 4-6hrs a day for a week when it gets a bit colder and set it to maintain around 22C and see what heat loss I get then. I will still speak to the builder to get a thermal imaging survey regardless as I’m convinced insulation is not sufficient. Radiator in master bedroom is 1066W (single convector) and nursery room is 1056W (double convector) and they are heating the rooms very quick unlike the old ones. I’ll upload the reports from the inspection so you can have a look and see if you can spot something wrong in there as I don’t know much about all.
 

Link 1

Link 2

Link 3

[Littlebig]

On 05/11/2022 at 13:14, MikeGrahamT21 said:

99% sure you’ll have dot and dab plasterboards on your walls, and this is likely a big contributor to your issues, take a socket face plate off on a windy day, if it blows a gale, we’ll I’m sure you can imagine what’s happening behind there…

Well thats I am a bit confused about.

When I put the light out in the garden when I cut out the square for the fused spur in the wall I could swear it was dot and dab as I could see it. On the other hand when I put an extra socket for the tv and a dryer up on the internal walls I did see it was batten. Not sure if its different for the internal and external walls?

[ProDave]

1 hour ago, Littlebig said:

Well thats I am a bit confused about.

When I put the light out in the garden when I cut out the square for the fused spur in the wall I could swear it was dot and dab as I could see it. On the other hand when I put an extra socket for the tv and a dryer up on the internal walls I did see it was batten. Not sure if its different for the internal and external walls?

Internal walls will likely be timber stud frame and plasterboard.  External walls will likely be dot and dab plasterboard onto blockwork.  The "problem" with dot and dab is usually poor workmanship and lack of understanding that somewhere there is a gap that allows cold outside air, usually from the loft, to get behind the gap between the plasterboard and the blockwork.  The term "plasterboard tent" has often been used to describe it.

[AliG]

As @ProDave says, cold air might be getting into the small space between the blockwork and the dot and dab plasterboard.

 

Where you put in the fused spur, you need to seal where the cable goes through the blockwork, so cold air is not getting ing in behind the plasterboard.

 

If you go up into the loft and check at the outside wall, you will be able to see if the small cavity between the blockwork and plasterboard is open to the loft which will let cold air in. If it is I would use expanding foam to seal the top edge.

 

There won't be much difference between blown in insulation and mineral wool. At least it means that it is unlikely the builders missed putting pieces in.

[Littlebig]

So I decided to have a look into my loft today just to see what is going on up there. I have managed to balance the temp. in the house by setting the heating to come on automatically twice a day for a total of about 120-150mins otherwise the house gets way to warm. What I noticed was a lot of condensation on the roof (across the full width above the bathroom and 2nd bedroom) which in my opinion is the answer to my issue. Looks like all the heat is escaping through the roof and I can’t work out why. If anyone has any suggestions as to what could be the problem please let me know. I am in the process of getting someone to come and do a full survey as I’m fed up

with the builder and after the inspection will decide which to go based on the findings.

[Littlebig]

Also I guess seeing daylight through the roof is not a good sign either?

[Roundtuit]

Heat will escape; insulation just slows down the rate.  Looks like you need more ventilation in the loft space to get rid of the condensation.  Perhaps check the eaves are not blocked with insulation.

[Radian]

49 minutes ago, Roundtuit said:

Looks like you need more ventilation in the loft space to get rid of the condensation.  Perhaps check the eaves are not blocked with insulation.

 

That's a serious amount of condensation right there - I think mould has formed on the rafters. That needs treating. But this is a cold loft with vapour permable roof membrane. My understanding is that these don't require ventilation at eaves level, with sufficient evacuation taking place on the upper side of the membrane. The gap in the membrane at the apex doesn't look intentional given the sloppy bunching. Again, ridge vents aren't always required for permeable membrane but they seem to be provided by default with dry ridge. I'm spouting all this in the hope that someone will step in and correct me if I'm wrong.

[AliG]

Daylight through the roof is ok as it might well be ventilation.

 

Your insulation is on the ceiling and it is then cold above it. “A cold roof”. In a cold roof design there should be adequate ventilation to stop condensation forming in the roof space. It can be in many places - eaves, ridge and tile edge for example. There should maybe be a vapour barrier at ceiling level to stop moist air getting up into the roof from the house, but if it is adequately ventilated I don’t think this is necessary.

 

So you definitely have something wrong there!

 

Looking at the picture of the house, my guess is that you have eaves ventilation(actually the spec says you do). Do you have grilles you can see in the underside of the eaves? If so the insulation should not go all the way into the edge of the roof as it would block the ventilation.

 

I would also be checking that you don’t have an extractor fan from the bathroom that is not ducted all

the way to outside. Quite often builders forget to connect them up.

[MikeGrahamT21]

Wow i've not seen that much condensation in a loft for a very long time. I would imaging a lot of it will have dripped down onto your insulation, making matters even worse. If you have a window vac, might be a good idea to suck as much of that water up as possible.

 

Check extractor fan connections, this is a common issue as has been said. There are also other options which you could look into, increase ventilation into the loft, some breathable membrane is better than others at releasing moisture, a couple of vent tiles wouldn't go a miss in yours. Bathroom will clearly be a major source of moisture, its highly unlikely you'll have a vapour membrane above the bathroom ceiling, you could remove the insulation and paint the back of the plasterboards with a liquid vapour membrane, something like black jack DPC may well work, just slowing down the rate moisture can escape through the plasterboard into the loft. Make sure there are no gaps from bathroom to loft, where light fittings are, if your extractor goes into loft etc. Any there, seal them up with good quality silicone.

 

Rafters without doubt need treating with anti fungal.

[Littlebig]

Thanks everyone for the replies. It is eaves ventilation according to the specs. I only had a look because of the ongoing heat loss issue and when I noticed the amount of condensation I knew something is not right. I am currently expecting a report from the builder investigation as to why reported issues had not been resolved but marked as complete.
Once I have a look at the report and what they have outlined as their next step, then I will make a decision on how to proceed with the urgent repairs.

[Andehh]

On 11/04/2022 at 22:48, Russell griffiths said:

There are companies that specifically look at faults in new builds. Look one up and get them to investigate. 
it’s a shame it’s getting warmer. Get a thermal imaging camera thing, crank the heating up and stand outside to see where it is escaping. 
or set up a home made air test, set a fan to suck air out of the room and stand in the room hunting for the cold draught. 

 

100% rent a thermal camera, and crank the heating up for an hour to so and then go exploring! Should only need it for an hour or two. 

Edited December 12, 2022 by Andehh

[Andehh]

Also to add, your second set of temp drops don't seem totally unreasonable in my book. Your bedroom would naturally be warmer if there are two adults asleep in it, the body heat alone will make a noticeable difference. 

 

Remember the Matrix films?

[Littlebig]

Hi everyone, just a little update on the issues mentioned above.

We finally managed to get the builder to do a heat survey and get a bit more details on what is going on with the insulation. Survey was conducted by the company blowing the cavity insulation in and the attending contractor gave a detailed explanation of his findings. The highlight of all was that he concluded there is a problem with draughts more than anything, so the report was sent to the builder and now awaiting repair.

In the meantime I changed the extraction fan in the bathroom and put a new external vent with a non-return shutter flaps to prevent cold air coming through. When I did that I was able to have a look in the cavity and took few pictures for someone knowledgable to say whether this is OK or not as I am not sure it is.

[Littlebig]

Just now, Littlebig said:

Hi everyone, just a little update on the issues mentioned above.

We finally managed to get the builder to do a heat survey and get a bit more details on what is going on with the insulation. Survey was conducted by the company blowing the cavity insulation in and the attending contractor gave a detailed explanation of his findings. The highlight of all was that he concluded there is a problem with draughts more than anything, so the report was sent to the builder and now awaiting repair.

In the meantime I changed the extraction fan in the bathroom and put a new external vent with a non-return shutter flaps to prevent cold air coming through. When I did that I was able to have a look in the cavity and took few pictures for someone knowledgable to say whether this is OK or not as I am not sure it is.

 

[PeterW]

Definitely not ok !!!! Should be full to the top..!!

 

installation will be warranted by the CWA (Cavity Wall Association) so they should take this up  

[Radian]

48 minutes ago, Littlebig said:

Survey was conducted by the company blowing the cavity insulation in and the attending contractor gave a detailed explanation of his findings. The highlight of all was that he concluded there is a problem with draughts more than anything, so the report was sent to the builder and now awaiting repair.

 

So the cavity insulation guy is saying draughts coming up through the empty cavities isn't their problem? 😵