Heat loss calculation/measurement?

[JamesJJJ]

There are lots of excellent heat loss calculators available for design calculations, but is it possible to measure/calculate heat loss from an existing building and then compare to any kind of benchmark?

 

 

If I know:

• The size of the building
• The amount of gas consumed over a time period (e.g. a week)
• The average internal temp during the week
• The average external temp during the week

 

 

Is there a way of calculating the average heat loss and comparing that to some kind of benchmarks?

 

Reason I ask:

My house is a modern house with MVHR (badly installed but corrected by me) and gas c/h. It appears pretty well insulated but I have already observed some air-leaks around doors/windows etc. Whilst I have started plugging those gaps it would be good to calculate the average heat loss and then compare to some benchmarks to see how good/bad the thermal performance of my house is.

 

 

TIA,

 

[JohnMo]

Calculate the the surface area of the building exposed to out air temp.

 

If you take the average delta between inside and outside. Write it down.

 

Take your gas consumption, you will need to remove a proportion for DHW heating based on number of people in house etc. Look up for details, but I think it could be about 4kW for 2.4 person house per day. Write it down.

 

Divide the gas consumption kWh, number days then by 24.  This give you a number kW you consume to heat house approx.

 

Now divide the exposed area by kW.

 

This will kW per M2., Divide by 1000 to give W/m2.

 

Divide W/m2 by the delta T.

 

This will give you and average U value (but will include ventilation losses, which should be quite small with MVHR).

 

A U value is W/m2.K

 

K is Kelvin.  Kelvin is deg C plus 273.  But as you would add 273 to internal and external temp, taking the number s as presented would be ok.

 

If you get below 0.15 your ok, if above 0.2, take another look at the numbers especially the domestic hot water use.

[SteamyTea]

Can you look up a few EPCs and find what the average is. They are only calculated numbers, and often in error, but gives you an idea.

You can work out DHW demand using Heating Degree Days. Again only a rough estimate, but somewhere to start from.