Thermal mass

A few friends have observed that our kitchen/diner looks like a small church hall, but it's not that kind of mass I'm writing about.

The last week or so has seen autumn finally arrive, with the pellet boiler being well used after a mild October. As a result the underfloor heating in the kitchen/diner has been in operation for it's first full week, and it shows. The floor comprises a concrete slab foundation, a layer of thermal insulation, the underfloor heating pipework, concrete screed and then limestone tiles as the finished floor. Hence the floor contains a lot of mass. The net result of this is that it has taken several days for the cold concrete and limestone to warm up once the heating system has started pumping warm water (At a temperature of 40 C) through it. However, once warm the mass of the floor retains this heat so that once the boiler stops firing it acts as a heat sink, slowly releasing heat into the house, much like a giant storage heater. So despite being a large open plan space, with plenty of glazing, the kitchen/diner is proving to be one of the warmest rooms.

The warm floor is also very comfortable to walk on. Human physiology is such that we are at our most comfortable with warm feet and a cooler head, yet in the UK and other cooler climates we've developed homes that are heated by hot panels mounted on the walls. Not only do these fail to warm our feet but they rely on high temperature hot water which is less efficient to produce. It's far more efficient to produce more warm water at a lower temperature and spread it over a larger area, such as the floor. This satisfies our need for warm feet, uses the concrete floors that so many homes have and keeps our walls free from the clutter of radiators.

Makes you wonder why we didn't think of this years ago...http://en.wikipedia.org/wiki/Hypocaust