BUILDING FABRIC & EXTERIORS
If you build a well-insulated and airtight home you could use HPV to provide a low energy heating system
heat-loss of a home, meaning half your heating bill goes to mitigating the effects of ventilation. So how do you guarantee good indoor air quality without losing heat? What types of ventilation are suitable?
Passive stack ventilation relies on natural air movement and a temperature difference inside and outside the home, so if it’s gusty there’s a risk of getting cold from over-ventilation and in the summer being stuffy, as temperatures are too similar in and outside for much air movement. Positive input ventilation relies on the house being leaky, so is not much good on the sustainability front. Mechanical extract ventilation relies on trickle vents, so you’re not only losing heat but it’s questionable whether you
can guarantee that CO2 levels will be kept under the recommended 1,000 ppm level. This is where heat recovery ventilation
(HRV) comes into play. A low energy fan unit continuously extracts stale air out of wet rooms while drawing in fresh filtered air from outside. The two airflows pass each other in a heat exchanger (not mixing) and up to 95 per cent of the heat from the stale air is transferred to the fresh air being put into the habitable rooms of the home via ductwork and ceiling terminals. Good HRV systems will be Passivhaus certified, have an automatic summer bypass (no heat recovery in hot months), trap pollen and
32
www.sbhonline.co.uk
allergens down to 0.01 microns, and save about a third on heating bills. They should also have a controller ensuring the system is perfectly set up for your house and lifestyle with a 24/7 timer, temperature monitors, a boost function, memory cards, and cold weather, reduced supply-rate function. However, even with the best HRV systems, there is still heat available to recycle. Heat pump ventilation (HPV) integrates a micro heat pump within the HRV unit to harness far more energy from the outgoing air. If you build a well- insulated and airtight home, you could take advantage of HPV and use it to provide a low energy heating system as well as ventilation. They can recover 100 per cent of indoor heat and, for example, the HPV Series system enables users to obtain between 3.5 and 12 kW of heat energy, from only 1kW of power. This option also has three different supply temperature zones, as you may want different temperatures in your bedroom and living room, for instance. Another useful option is a heated ceiling terminal supplying quick-reacting top-up heating to a particularly cold room. The added bonus of HPV is that it can also provide cooling – useful on sticky summer nights. That just leaves you to find a low energy domestic hot water source – the HPV Series includes a micro heat pump integral to a 300 litre water tank, so you
get heat recovery ventilation, very energy efficient heating, cooling and hot water all in one system. This type of system will be seen in practice when the Build It Education House at Graven Hill in Bicester is finished. For more ‘petite’ homes, compact service units provide HPV with a smaller water tank integral to the unit. It is important to ensure that the ‘veins’ of the system are correct – the ducting to each room. Rigid metal safe-seal ducting of 100-125 mm is best for airflows and hygiene (plastic isn’t naturally antibacterial) and is very robust on site. It also needs to be insulated correctly otherwise heat will be lost. The principle behind heat pump ventilation and heat recovery ventilation is firmly grounded in the drive for more healthy, sustainable and convenient living. Perhaps all you need is the air that you breathe, to provide low energy heating, cooling, ventilation and hot water.
Clarissa Youden is associate director at Total Home Environment
may/june 2019
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60
