Replies

1. GBA Editor
   Martin Holladay | Jun 04, 2015 06:57am | #1

   John,
   If you are comfortable heating only one or two rooms of your house at a time rather than heating the entire house -- or heating individual rooms for only a few hours a day, when the rooms are occupied -- that approach will save energy compared to heating the entire house for 24 hours per day.

   That said, the method of heating I just described -- still common in some parts of Europe, Japan, and the Middle East -- is rare in the U.S. Most people are willing to pay for the heating fuel required to keep every room (or almost every room) in their home comfortable for 24 hours a day.

   Whether or not you want to have a centrally heated house that stays warm all winter long depends on (a) fuel costs in the U.K., and (b) your budget. If you can afford central heating, it is certainly more comfortable.

   It sounds like your exterior walls are fairly well insulated. There remain several ways that your house may still be losing heat. These include (a) heat loss through old single-pane windows, (b) heat loss associated with air leaks, and (c) heat loss through a poorly insulated attic (or loft, as your probably call it).

   Here in the U.S., we have home performance contractors (or energy auditors) who can visit a house to check on these aspects of a thermal envelope. If you have that type of contractor in the U.K., and you've checked all those items, that's good.

   So, if you have tightened up your house, and if you have storm windows or double-glazed windows, and adequate loft insulation, you should heat up your house to a comfortable temperature (21°C or 22°C) in October and keep your house at that temperature for 24 hours a day until late April or early May -- unless you can't afford to do so.

2. 
   user-2890856 | Jun 04, 2015 07:23am | #2

   Your largest problem is that you have a large object or mass that is well below the temperature you are trying to maintain in the rooms . As long as the walls are 11*c (51.8*F) heat will continue to be absorbed by those walls located inside the thermal boundary where you want 20*c . In the beginning of the season if you heat that mass it will be easier to maintain a mean radiant temperature throughout the season .
   You will not be losing your natural heat to cold surfaces all year and turning up the heat because you feel cold . It takes less energy to maintain something than coasting then accelerating , similar to driving your auto in stop and go traffic as opposed to on the highway where you get your best efficiencies .
   raise the temp of the mass to 17-18*c and maintain about 20*c in the house in some fashion .

   Mr Holliday brought up some very good points about insulation that will help you lessen your losses to the outdoors . Now that you have installed insulation on the exterior of the walls though you cannot ignore their need for heat . If you heat that mass you will lower the Delta T ( Ti >To ) . The narrower that differential the less heat transfer will occur , while lessening the heat lost by your body due to being in proximity to a cold object . This will increase your Comfort while lessening the amount of heat being absorbed by the walls , heat being absorbed by and transferring through them will never do you any good .

3. GBA Editor
   Martin Holladay | Jun 04, 2015 07:30am | #3

   John,
   What Richard is saying is that the first time you turn on the heat in October, it may take a few days to raise the temperature of your masonry walls to 20°C or 22°C.

   Once these walls are heated up, however, the 4 inches of rigid foam on the exterior side of the walls will keep the walls warm, and the heated thermal mass will act as a useful flywheel to keep you comfortable all winter long.