How a House Party Can Help You Understand How To Reduce Your Fuel Bill

Hopefully, we have all experienced a good old house party. The best one I had was when I hosted one while my parents went on holiday with my youngest brother leaving their 17 and 18 year old sons at home for two weeks. It was a well-planned party (even had a beer tent…which the scooter/motorbike fraternity set on fire to ride through) apart from we didn’t factor another party on the same night at a local residential college getting shut down and all the revellers coming to ours. A few hours later, seven police cars turned up to give around 300 people who had been drinking a 10 minute amnesty to leave…even allowing them to drive their cars. It was 1989. But I digress.

So how does a party illustrate how we should all be heating our homes? Well, it has something to do with body heat which as you know is 37C and power. But first some maths. I’ll try keep it simple. 

The average home in the UK (despite them being called leaky) needs 8,000 joules of heat per second (otherwise known as 8kW of power) to maintain an internal temperature of 21C when it is a bitter -3C outside.

The difference between -3 and +21 is 24. We take this 24 and divide our 8,000 watts (8kW) with it. This equals 333 recurring. Let’s call it 333 to keep things simple. This is our HTC (heating transfer coefficient) number which we can now use to determine how much heat we need at any outside temp. If it was 10C outside, the difference between 10 and 21 degrees is 11. 

11 multipled by 333 equals 3.663. This means we would need 3,663 joules of heat per second (3,663 watts of power or 3.663kW) to maintain an internal temp of 21C inside when it was 10C outside. 

Let’s do another: it’s now 5C outside. If we multiply our HTC of 333 by a temp difference of 16 (5 degrees to 21 degrees is a difference of 16) we get 5,328 watts (5.328 kW). So we now know our home needs 5,328 joules of heat per second to maintain it at an internal temp of 21 degrees. Now for the party.

The human body gives off around 80 watts at rest. But we are at a party, so hopefully we are all moving meaning we give off around 100 watts. To maintain the internal temperature of 21C when it was -3C outside I would need 80 people jumping around: 80 people x 100 watts = our 8,000 watts.

If we had partied all through the night and the sun was coming up and it is now 10C outside I only need 36 people’s body heat to maintain the required 21C inside. 

I could keep booting people out and inviting them back again according to the temp outside. This is called weather compensation and we should really be using weather compensation or load compensation on all our heating systems. An important thing to remember is that our party is a low temperature heating system with a flow temperature of only 37C (body temperature).

Presently, and as far as I know, we don’t yet have the technology to keep a heating system’s flow temp at a constant 37C and have shapeshifting radiators which can grow in size depending on the outside temperature to give us the required power. People coming and returning to the party is the same as increasing and decreasing the surface area of radiators. But what we can do in a compensated heating system is to modulate the flow temperature from our boiler or heat pump to match the demand the home needs depending on outside temperatures.

Compensation control has existed since the ’70s yet it is tragic that most the boilers being installed are with a fixed flow temp. There has been some good recent advice on how to reduce your flow temp on a combination condensing boiler. In reality all our boilers should be controlling their own flow temp and constantly changing it according to the outside temperature. This gives greater efficiency and will lower your fuel bills. 

So, next time you have a boiler installed, demand compensation controls and do not be duped by smart stats. Smart just means they can connect to the Internet. Some smart thermostats can actually modulate the boiler flow but others can’t.

I hope that this helps you understand two things:

1) We don’t need ridiculously high temperatures to heat a home (the wall thermostat was invented because the home would get too hot and the boiler had to be shut off).

2) Your boiler’s flow temperature should ideally be modulating

Last passing request: please drink responsibly at your next “house warming party” and look out for each other. There is still much fun to be had in life.

In case you’re wondering what happened at our party, about three of our parents’ friends had to bring their carpet cleaners around and we’d thought we were clever locking every ornament, painting, photo, plant, etc. away in our parent’s room. I had nailed it shut from the inside then jumped out the window. When we came to put it all back, did we know where it all went? Not a clue. Mum instantly knew when plates that had been on the Welsh dresser were now somewhere else and photos and paintings from the lounge were hung in the hallway. Oops.

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Graham Hendra
1899 kWhs
1 year ago

i like it nice and simple to follow

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