Part of the BRE Trust BRE: Investigation into Longtown Heating
Systems David Butler 9 October 2014
Slide 2
Part of the BRE Trust BRE Building Research Establishment Ltd
BRE is an independent research based consultancy, free of
commercial and government interests and is owned by the BRE Trust.
The BRE Trust is a charity and all of BREs profits go back into
research and education projects supported by the BRE Trust. BREs
scope includes buildings, the environmental, fire, security and
safety.
Slide 3
BRE was commissioned by Riverside to undertake an independent
investigation: 1.Are the new heating systems suitable? 2.Were the
systems and specifications appropriate? 3.Are the running costs
(electricity bills) reasonable or not? 4.Do the solar PV
installations affect the heating systems? BRE investigation into
Longtown Heating Systems
Slide 4
Scope of BRE Work Two BRE specialists: Heating expert - David
Butler Solar energy expert - Steve Pester Visited and inspected 5
representative Longtown properties in May 2014. Provided a detailed
report on findings and recommendations to Riverside
Slide 5
Choice of heating system Riverside has provided modern whole
house radiator based heating systems. Mains gas is the cheapest
fuel and the standard choice. Lack of mains gas in Longtown
restricted the options. BRE confirms that electricity is best fuel
for Longtown but is more expensive than gas. Oil, LPG, propane are
alternatives but are expensive, have safety and storage issues and
potentially large and unpredictable price fluctuations.
Slide 6
Choice of heating boiler - ASHPs Air source heat pumps (ASHPs)
can replace conventional boilers. ASHPs pump heat from outside they
provide 2x to 3x the amount of energy consumed to run the machine.
Running cost of an ASHP is similar to a gas boiler.
Slide 7
Choice of heating boiler electric boilers Some Longtown
properties are not suitable for ASHPs Flooding risk and strength of
house walls. Electric boilers have been used instead.
Slide 8
Cost of running heating systems Whole house central heating
provides high comfort levels and convenience. But, must be
controlled sensibly to avoid high heating bills.
Slide 9
Heating bills Most tenants appeared to be on standard
electricity tariff or Economy 7 (E7). Standard tariff is not
usually suitable for electric heating. E7 is designed for storage
heaters. E10 is designed for electric boilers. BRE has advised
Riverside to help tenants choose most suitable tariff.
Slide 10
Electricity tariffs E10 off-peak rate - 5 hours overnight, 3
hours early afternoon and 2 hours in the evening. May not suit all
tenants. Heating system programmer times should be set to heat
house as much as possible during off-peak times. Hot water timer
should heat hot water only during off- peak hours.
Slide 11
Electricity tariffs E10 is not available from all suppliers.
EDF and SSE offer E10. Check peak and off-peak prices there may be
a difference between suppliers. Total savings from switching to E10
may be 15 to 20% a year. Some tenants will need help in switching
to most appropriate supplier and tariff and in setting
programmers.
Slide 12
Solar PV systems
Slide 13
BRE inspected 5. All were wired & working as expected.
House electricity meter only registers what electricity is consumed
from the grid. A second electricity meter shows how much energy has
been generated by the PV. BRE confirms no interaction is possible
with the heating systems. Incoming from main meter PV generation
meter and PV system PV AC isolator
Slide 14
Solar PV systems BRE confirms solar PV systems are working well
(4.7 kWh / day in May in one property inspected by BRE). PV
electricity is free to tenant but any surplus power goes to the
grid.
Slide 15
Making the most of the free PV electricity Most PV electricity
is generated on sunny days when most people use least energy so a
lot may be exported to the grid. A special Power Diverter can be
fitted that diverts PV electricity to heat the hot water tank a
form of energy storage. BRE recommends that Riverside considers
installing Power Diverters so that tenants benefit more from the
solar PV.
Slide 16
Improvements to insulation and windows The Riverside properties
are 60 years old - heating bills can be reduced by improving
thermal insulation. BRE recommends that Riverside continues with
investment in improving insulation, e.g. external wall insulation
and new windows. Any defective pipe and loft insulation (BRE and
Avoca found some missing or defective insulation) should be
rectified.
Slide 17
Conclusions Riverside have provided tenants with a modern whole
house central heating system >> higher comfort &
convenience. No mains gas in Longtown means that more expensive
electricity has to be used instead of gas. ASHPs use electricity
very efficiency (provide 2x to 3x the energy) but not suitable for
all houses. Electric boilers are usually cheaper to run on E10.
Solar PV provides tenants with some free electricity but the amount
may be increased by fitting Power Diverters. Further investment in
insulation and help in setting controls and choosing best tariffs
will reduce tenants energy costs.