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Energy Assessment: Low Internal House Temperature

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  1.  
    • CommentAuthorjo10000_6
    • CommentTimeApr 8th 2009
     
    Dear Green Building Forum,

    I am looking for advice of how to handle/progress my problem.

    In this day and age of wanting to be as green as possible and at the same time attempting keep energy costs under control I was fairly comfortable that when I purchased a new 4 bedroom house 4 years ago that I was buying a house that was reasonably energy efficient.

    Perhaps assumption that I had bought a reasonably energy efficient house (SAP Rating 101/120) made me ignorant to the fact that I hadn’t.

    I have spent over a year researching “U” Values / “R” Values, Cavity Wall Insulation, BTU’s just to try and understand why my house is so cold – we are not talking a one-off room – we are taking within a degree the whole house being the same.

    To put it into perspective, as you know the temperatures over Christmas dropped to 0 Degree’s. My house, without heating would be approx 10.5-11 Degree’s internal inside temperature. A relative’s house, approx 35 years old with cavity wall insulation installed a few years ago would be approx 17-18 degree’s. Therefore I would take approx 1.5-2 hours to get from 11 to 19 whereas they would take less than 30 minutes to get to a nice temperature. After asking questions to numerous people I now realise that something is wrong – forget about “U” Values and take it as being as simplistic as my starting internal temperature is far to low to be right

    Now, as the temperature starts to increase, my internal temperature is still less than my relatives house at Christmas, even though the temperature outside has risen to 10/11 degree’s my inside temperature hasn’t gone past 15.5. In fact it appears to stay at 15.5 even when it gets to 12 outside.

    What do I do ? Do I have any comeback….I prepared to make a nuisance of my self but where do I start. Any advice / suggestions appreciated.
    • CommentAuthorchuckey
    • CommentTimeApr 8th 2009
     
    I can't quite get my head around your figures. You said that the outside temp. was 0 deg C and your internal temperature was 10.5 + deg C. So what was causing the 10 deg C increase in your temperature without any heating?. Normally its waste heat from light fittings, cooking, bodies, baths etc. So total this lot up and come to some figure say X Kw/hrs. From this you can work out that your house requires .X Kw/hrs per degree C heating. So your second comment "the house is at 15 deg C when its 12 outside", does not make sense unless you are not using so much "stuff" and generating so much waste heat.
    The time factor of running a boiler and when the system reaches a steady temperature is a question of how big a boiler and how small a house. In your relatives house if the boiler was sized for pre-cavity insulation, saving 30% of the heat losses through the cavity will have effectively overated the boiler by this 30%, hence the shorter time period.
    Frank
    • CommentAuthortony
    • CommentTimeApr 8th 2009
     
    What is the construction of your house? is it "dry lined"? is it colder when it is windy outside?
    • CommentAuthorjo10000_6
    • CommentTimeApr 8th 2009
     
    Hi Frank,

    When I have done the checks on internal temperatures - they are literally as i wake up - 7.00 ish - before anything is switched on (ie lights and no cooking etc). I "assume" the 10 dgree difference is caused by the insulation in the house ? When I check my relatives house again - early - no cooking or lights etc and my cousins are still in bed so no body movement causing too much heat.

    Lets ignore the boiler comment for the time being - are you suggesting that with no heating on, not cooking or lights my house should beless than 10.5. ?

    Im am interested in other people's inside temperatures (prior to heating) to compare.

    Hi Tony, My house is brick and block ...not sure about the dry lining...it dosent feel colder when its windy - probably because it feels cold all the time !
    • CommentAuthortony
    • CommentTimeApr 8th 2009
     
    are the walls hollow sounding when tapped?
    • CommentAuthorCWatters
    • CommentTimeApr 8th 2009
     
    Jo10000_6,

    How do your heating bills compare to someone with a similar size house and lifestyle?

    Consider replacing the thermostat with a programmable one that will allow different temperatures to be set at different times of the day. For example..

    11pm to 6am = 16C
    6am to 8am = 20C
    8am to 5pm = 16C (or off?)
    5pm to 11pm = 20C

    You could also consider getting the house pressure tested to see how draughty it really is. It's possible to have a large number of small air leaks (around skirting boards for example) and not notice specific draught.
    • CommentAuthorPaulD
    • CommentTimeApr 9th 2009
     
    I think you're confusing a number of things here.

    Firstly if the house was uninhabited over a period of time the average internal temperature would equal the average outside temperature over a period of time.

    The only thing that can change this is the insulation properties and thermal mass. For example if the daytime temperature was 10 by the end of the day the internal temperature would also rise. similarly it would fall during the night.

    Your problem compared to the neighbours is the rate of change. the neighbours house is clearly either better insulated and/or has a higher thermal mass. probably a combination of both.

    Either way improving the installation will help, particularly if you can do this internally as this will reduce the thermal mass.

    regards
    Paul
  8.  
    hi,
    The speed it cools is exactly as per all the other heat transfers in that it logarithmic wrt one temp and the other temp. So the initial cooling will be faster than the latter. If the house was at 20 deg it would cool to 15 deg much faster than it would from 10 deg to 5 deg. This is because the rate of heat transfer (power) depends on the temp difference.
    I have found the same thing that with no heating it will level off at 10 – 12 deg and does eventually go below 10 deg only if there is a very long period of sub zero and cold days as well.

    It will of course depend on many other factors such as draught proofing and damp conditions which will suck the heat out of anything.

    Cheers, Mike up North
    • CommentAuthortony
    • CommentTimeApr 9th 2009
     
    I didn't agree with the notion of the house falling to outside temperature -- even unoccupied it will always be a little warmer inside than outside due to it heating up from solar gain during the day and never quite loosing it all through the night.
    • CommentAuthorbrig001
    • CommentTimeApr 9th 2009
     
    I am not sure if thermal mass explains the difference here, because it takes a long time to warm up implying a high thermal mass, conversely it cools quickly implying a low thermal mass. Sounds more like a fault in the building itself, possibly draughts behind plasterboard or under floors,

    For info, all through winter, the house did not lose more than 2 degrees C from 22:30 (21 degrees C) to 6:30 (12 year old 4 bed detached, brick/block filled cavities).

    As for what you do about it, I would fix it myself, but I am paranoid and wouldn't trust someone when they had messed it up once already, and I am handy with a circular saw (I know paranoia and a circular saw...).
  11.  
    I reckon your radiators are too small. I'm putting 2 & 2 together on this & guessing. What I would suggest is using one of the boiler sizing programs on the web to give you room by room energy requirments. Then use something like the stelrad website to give you radiator sizes/kW ratings. COmpare and contrast.

    Even if i'm wrong it will give you something to work on.
    • CommentAuthorjo10000_6
    • CommentTimeApr 22nd 2009
     
    Just want to thank you for all your comments and just answer a couple of questions (been away - sorry). I supposse Im satisfied that there can be definative answer/solution but again, thank you.

    Hi Tony,

    You mention are the walls hollow when tapped – do you mean internal ones ? Which, yes some of them do but I’m assuming it’s because they are partition walls.

    Hi C Watters, I have a programmable thermostat. Your temperature suggestions are worth trying but my house is often less than 16 degree’s and I suppose I’m concerned about the boiler running continually on/off.

    Is a pressure test an expensive thing to do ?

    Hi Paul,

    Appreciate your comments. Regarding the comparison in houses – my comparison in internal temperatures – on the same day at the same time – is actually a relatives 35-40 year old council house. That’s why I’m struggling to understand where I can top up on the insulation – if my 4 years old houses don’t have as much, if not more than her’s then perhaps I bought the wrong house.

    Any suggestions though on top’s up very much appreacited!


    Hi Brig001,

    You’re spot on …long time to heat seemingly quick to cool. Would the pressure test that Tony suggests pick up on the drafts – the thought of circular saws scare me ! ps wish I had your house !

    Hi Dimengineer – I think the radiators are ‘correct’– i.e. they more or less exactly match up to the Stelrad Stars Disk that I had for calculating BTU’s – in my opinion if they were of the limit I would probably have gone one size up. Unfortunately the system is micro bore and the people that installed them fitted them so close to the wall that if I want to go bigger it’s actually a very big job to change with some re-plastering of the walls thereafter. It’s a bit of putting when there are a few radiators.
    • CommentAuthortony
    • CommentTimeApr 22nd 2009
     
    I was asking about the inside of the outside walls.
    • CommentAuthorbrig001
    • CommentTimeApr 22nd 2009
     
    Hi jo10000_6, not necessarily. The floor (and walls) might be sealed to each other making the inside envelope airtight, but cold air can still get to the other side making it cold. If the underside of the floorboards was ventilated, all you have for insulation is the boards themselves. The same is true with plasterboard on walls. So at the worst case, your walls could be plasterboard and the floors wood with cold air on the other side of both.

    These problems are common in the UK, but can be fixed or drastically improved, but I suppose that the point is that you shouldn't have to.
    • CommentAuthortrule
    • CommentTimeApr 22nd 2009
     
    Sounds like you don't have a fully insulated house. Do you have any insulation in your loft? Under the floor. Should be easy to check. Sometimes the insulation its there but its not correctly fitted.

    I had a house with a vented floor space, un-insulated, and single pane glass. Night time temps in the house got down to around 10 degC with outside temp of 0 degC. Took all day to get the temperature back upto 20 degC

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