How do I measure the amount of heat used by a building?

Question

I need to measure the amount of heat energy used in a building which includes radiators and hot water usage. is there a simple way to do this? if I measure the temp difference between the flow and return pipes from the boiler do I also need to know the flow rate and if so how do I measure it?
Thanks in advance.

Answer 1

I'd just look at the gas meter twice, once at the start of the month, once a month later.



If you know the heat output of each water heater or furnace, you could integrate the on/off cycle time using a bit of calculus, and multiply the duty cycle by the rated output, for near real time measurement.

Answer 2

The easiest way is to get the electric bill and the gas bill.



The amount of gas the building used can be converted to BTU's per cubic foot of gas consumed. By using this method you are also taking into account the gas exhaust heat that went up the chimney but still needs to be part of the inputted energy. So for example if 10,000 cubic feet of gas was used at 1,000 BTU per cf then the building used 10 million BTU's of heat from the gas alone.



Then you have to add the electricity usage. All electric use inside a building gets converted to thermal energy after its purpose has been accomplished. Clocks, electric motors, light bulbs, appliances, etc all just give up their energy as BTU's of heat. SO for example the building used 1,000 kwh of electricity in that month, then convert that kilowatts to heat (either BTU or metric)



One kilowatt hour of electricity = 3,413 BTU's of heat

1,000 kwh * 3,413 btu = 3,413,000 BTU's of additional heat



So using the above building example of 1000 kwh of electric a month and 10,000 cf of gas consumed this building used :

10 million BTU (from gas) + 3,413,000 BTU's (from electric) = 13.413 million BTU's of heat used



If you measure at the sources like you plan, you will miss the chimney losses of the gas heater and boiler and pilot lights. Plus the heat from the use of appliances isn't insignificant.

Answer 3

Put AC current meter on every heating equipment,recording down their total running time and amperes. Calculate the wattages and add them together.