Wednesday, August 29, 2007

There's a Hole in the Bucket


I am still waiting for promised Information from the company making the Super Efficient Electrical Heating Claim. In the meantime I will discuss some basic principles of heating, to the best of my limited knowledge.

The Leaking Bucket Principle

Heat loss is to a room or a house, as a leak is to a bucket of water. The bigger the hole in the bucket, the more water you will have to keep poring to keep it full.

A poorly insulated house is like a bucket with a great big hole in it. You have to pour in a great deal more just to keep it topped up.

Every building, no matter how well insulated, has some heat leakage. A superbly well insulated house would be like a bucket with a small hole in it - say a 2 or 3 mm hole. It is fairly easy to keep it topped up. A poorly insulated house is like a bucket with a great big 50 mm hole in the bottom. It is very hard indeed to keep up with the amount needed to keep it full, because it just pours away so fast.

Older houses tend not to have good insulation and fall into the letter category. There is usually no cavity insulation, sometimes no cavity either in the walls. Most older homes don't have double glazing, or good attic insulation. Nor do they have under floor insulation. This type of house takes a huge amount of heating just to keep it passable warm.

What are the principles involved in this Super Efficient Heating Claim?

The company are claiming that their figures are for fairly average houses, specifically not very well insulated homes. Perhaps houses equivalent to the bucket with a 15 to 25 mm hole in the bottom. Just to keep the bucket topped up it takes a fair flow of water, or in the case of the house, a fair flow of electricity, oil etc.

Heat loss, as the leak in the house bucket is called, can be measured in Kilo Watts or BTUs (British Thermal Units)

There is no escape from heat loss, and to replace the lost heat, it takes a pre-determined amount of power for a given size of room with a given amount of insulation.

Just like if there is a bucket with a leak so it takes say 4 litres per minute to keep it full, any less flow of water and the bucket will just gradually empty. Same with a room with a given heat loss, you gotta put in what is lost to maintain the temperature.

This company's claim seems to be contradicting this bit of accepted heating science. Or maybe I am missing something???

I am waiting to hear more, and as soon as I do I will let you know.


No comments: