eco & energy efficiency
How Heat Recovery Ventilation (HRV) works © Total Home Environment Ltd
Case study – Grandy’s Croft
Project: 1960’s block of six community housing flats in Solihull
Brief: With minimal disruption to residents:
• Regenerate to nearly zero carbon • Eradicate fuel poverty • Reduce internal maintenance • Regenerate local community
Aims:
• Achieve 85 per cent savings on heating bills
• Obtain EnerPHit certification • Prove all-in-one approach can work for large-scale roll-out
Retrofit Solution: OWLS (Off-Site Wrap-Around Large Scale Retrofit)
Partners:
Total Home Environment (HRV), Beattie Passive (TCosy), Encraft (energy consultants), Solihull Community Housing (owners) and Coventry University (monitoring)
What is heat recovery ventilation (HRV)?
Whole house ventilation is completely controlled to provide the correct amount of fresh air, when it’s needed and with great heat recovery. A fan unit located remotely continuously extracts stale air out of wet rooms, while drawing fresh filtered air from outside. They pass each other in a heat exchanger (not mixing) and up to 96 per cent of the heat from the stale air is transferred to the fresh air being put into the habitable rooms of the home. It gets rid of all the VOCs (Volatile Organic Compounds) – a cocktail of chemicals that leaches out of sofas, carpets, laminates, cleaning detergents etc. The main benefits of heat recovery ventilation include:
•Constant fresh air, filtered for pollen •VOC’s/CO2
removed for a healthier environment in which to breathe
•Heating bills reduced by about a third •Quiet operation •Decreased humidity levels, so less inviting for dust mites
•No condensation, so mould and mildew don’t grow, prolonging the life of the building fabric •Exceeds Building Regs
Things to look out for in an HRV system, if you want to put what’s said on paper, into practice:
•PassivHaus certification •EC motors •Automatic summer bypass •Heat recovery figures over 85 per cent •Rigid metal ducting where possible, which is best for airflows and hygiene
•Correct ductwork insulation •Controller with 24/7 timing, temperature monitors, SD card for data monitoring, anti-tamper lock out switch.
If you want to put paper into practice make sure you have control
Something else to contemplate in your retrofit is your heating strategy. If the heat-loss calculations still show a need for a formal heating system despite a retrofit plan, you can get your properties off electric or oil by investigating sustainable heat sources. This would include things like air-source heat pumps or biomass boilers where you can get money back with the Renewable Heat Incentive (RHI). It would certainly be worth it, if a gas boiler needs replacing, as air-source heat pumps can be at least three times more efficient. Also, with renewable heating there are no yearly gas certificate updates required and you won’t have the worry of possible carbon monoxide poisoning situations. If you have to keep the current heating
38 | HMM March 2016 |
www.housingmmonline.co.uk Summary:
A deep retrofit providing a new external insulated fabric, with new triple glazed windows and doors and mechanical heat recovery ventilation. Pre-monitoring of energy usage, temperatures and indoor air quality to continue into post-installation to assess actual impact of retrofit.
system, you can always reduce your reliance on it by providing air-to-water heat pumps just for domestic hot water, which means the formal heating system doesn’t need to be on in the warmer months. Some air-to-water heat pumps even have a secondary coil allowing connection to solar panels for free hot water – so if you’ve got lots of roof space, solar thermal panels may be a consideration. Depending on how far you’re going with your retrofit, there are even compact service units on the market which provide HRV, some providing space heating and domestic hot water all in one unit. These EnerPHit principles are firmly grounded in
the drive for sustainability and reducing our reliance on fossil fuels. We desperately need to make the fabric of our old housing stock better, but in doing so we need to combat the ‘cling-film effect’ by providing adequate ventilation for clean indoor air, without losing heat. Obviously, to alleviate fuel poverty, the more heat we recover, the less we need to generate.
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