Why is my home so expensive to heat?
A couple recently moved into their 5 bedroom 1970s built home. We will call them Steve and Shamila (not their real names though).
Background info
The building:
- Walls are brick cavity aircrete (Celcon) with lightweight plaster. No cavity insulation.
- The windows and doors are PVCu and about 15 years old. Mock Georgian small paned windows. Patio doors in the lounge and another set in the dining room. No enclosed porch / lobby area. Front door hardwood and varnished with applied brush draught excluders.
- The central heating is an indirect gas fired boiler (that means they have a hot water storage cylinder with header tanks in the loft). Boiler age approx 15 years old wall mounted. About 50% efficient at best. Room thermostat, hot water cylinderstat, hard wired control system wall mounted in hallway.
- A pitched roof with concrete pan tiles covering. Trussed roof structure. Loft has been boarded out using sheet chipboard screwed to the truss tie bars / ceiling joists. Minimal, old fibreglass insulation visible near the eaves where the boarding had been finished. Looks about 50mm thick at best.
- Solid ground floor
Furnishings: Fitted carpets and lightweight curtains left by previous owner.
The family: The couple: both out at work all day. 2 Children at school age. No pets
The Problem
They have now lived in the house almost a year. Their heating bill for gas and electricity is very expensive. The previous owner had shown her bills and said that the house was warm and her bills were low.
The difference: One lady who lived in the house on her own as her children had left home. Her husband had recently died - reason for selling the large house. Most of the time the lady was either in her garden, or watching her tv in the lounge That was the main room that had the heating turned on apart from the hallway and her bedroom. Most of the other rooms had the radiators turned off. One person's washing and drying it on a clothes line. One person's use of water for the loo, showering, and the washing machine would be quite small.
In contrast: All the rooms had the heating turned on. The thermostat set at 22°C. 4 people's washing and mostly tumble dried. Some wet washing draped over a clothes horse in the kitchen whilst out at work.
4 people showering and using towels to dry themselves off. Mum and daughter both had long hair.
The Budget:
Steve phones to ask whether having cavity wall retro insulation is a good idea. He has a budget to keep to, but his heating bills are very high. He would like to make the most of any improvements.
Substantial savings are needed on the energy bills. They must be cost effective though.
Is it worth having cavity wall insulation retro injected?
It is a large detached 5 bedroom house. The first issue is humidity.
Water can also be in a vapour form. Still H2O and requires a lot of energy to heat it up. (There is another blog presenting the science). A house with all the windows and doors shut most of the time (the family are out all day) cannot get rid of the moisture.
What moisture?
- 4 people breathing produces a lot of moisture. Ona very cold day you may notice the moisture coming out of people's mouths. That is happening 24/7. Where is that moisture going? Condensation on the windows? Soaking into all the soft absobant furnishings - the bed / mattress, sofa, curtains, carpets and so on. However, as the air in the house will probably be warmer than outside there will be a difference in air pressure. Air expands as it becomes warmer - if the walls and windows cannot move then the air will be pushed through the walls. The walls will become moist as the humidity condenses.
- The 4 showers each morning and 2 in the evening have produced a massive amount of water vapour. Even with an extractor (their house didn't have an extractor in either bathroom or the ensuite) there is still a massive amount that goes into the house.
- The cotton towels. They have just dried 4 bodies and 2 more for the girls hair. That is a lot of damp towels that will dry off during the day (if you are lucky). Where has all that moisture gone?
- All the condensation on the walls of the bathrooms and ensuite. Left to dry off / evaporate whilst all the windows and doors are closed and the heating is turned off. (Daft heating the home is everyone is out of the house).
- That washing hanging over the clothes horse in the kitchen. All that moisture evaporating off during the day.
Yes, if you collected all that moisture it would fill several pint glasses. Now consider heating that water to 22°C and maintaining that temperature. It would take a lot of energy. However, that is what is happening every day 365 days of the year.
The answer for stage 1
Drying the whole house out with a dehumidifier. Dry materials are easier, and therefore require less energy to heat up. Damp materials soak up energy. Wear a dry tee cotton shirt and you feel warm. Wear the same tee shirt when it is damp and you will feel cooler.
The air is in contact with most things in the house. The temperature of everything it is in contact with will become the same temperature - in equilibrium.
Dending upon the amount of humidity there has been in the house will determine how much water will need to be remove. Typically a house that has condensation on the windows will produce 2 to 6ltrs of water in the first 24hrs. Then, over about a week or so, the amount of water being removed will reduce down to nothing. At that point it will be about 40 to 45%RH.
If, after say 2 weeks of having the dehumidifier running it is still pulling out a significant amount of moisture then further investigation is required.
Stage 2 - Further Investigation
There are likely causes:
- The extractors in the bathroom / shower room / ensuite / kitchen are not working (clogged up with lint and dust, or cooking fat)
- Extractors not being used (Common issue in the summer when the light is not being used and the linked in switch to the extractor cannot work)
- The rooms do not have extractors
Check if the cooker hood is an extractor or a recirculator. An extractor will have a vent that send the humid air during cooking out of the building. A recirculator looks very similar, but the air is directed through a filter and back into the kitchen. No humidity is removed from the room though. The filters are designed to catch airborne fat.
Stage 3 - Drying out towels after bathing
It is surprising how much water is dried off our bodies and from our hair after bathing. As an experiment weigh the towels before you use them. [It is easier to put them in a bowl and used the kitchen scales]. Note the dry weight in grams. Then have your