HEATING, VENTILATION & SERVICES FOCUS


Pump up your indoor air quality


Clarissa Youden, associate director at Total Home Environment, provides a guide to ventilating an energy-efficient, airtight home, going beyond MVHR with heat pump ventilation technology


P


eople spend 70% of their time at home, meaning they breathe over 10,000 litres of air per day. It’s easy to assume that cracking open a window or two will keep the air inside a home pretty healthy. Sadly, that’s not always the case and a lot of heat (that’s cost a lot to produce), is lost in the process. As homes are sealed and insulated


indoors, without ever thinking about it. The air humans breathe out is about


more to keep the heat in and the cold out, the indoor air quality (IAQ) deteriorates. Unfortunately, lots of the items in a home leach out a cocktail of chemicals called VOCs (Volatile Organic Compounds) – things like carpets, curtains, sofas, laminates, cleaning detergents etc. Without controlled ventilation, most people will also live with high carbon dioxide (CO2


) levels


100 times more concentrated in CO2 than in Earth’s atmosphere and studies have suggested that over-exposure can reduce cognitive and decision–making performance by 50% or more at common indoor levels. High CO2


levels during


the night also result in restless sleep, headaches, a dry mouth and sensitive skin. But a solution is available.


Typical temperatures achievable for fresh filtered air when recycling heat with HRV/MVHR HRV & MVHR


Heat Recovery Ventilation (HRV) is a system that facilitates a ‘whole house’ air change every two hours, without losing heat. It works by taking stale, polluted, moisture-laden air from kitchens and bathrooms via ductwork and ceiling terminals and replacing it into living and bedrooms with fresh, filtered air from outside. Up to 95% of the outgoing air’s heat is recovered via a heat exchanger and transferred to the fresh incoming air. This heat recovery means less electricity, gas or oil is needed to heat your home. In summer, the heat exchanger within the unit can be bypassed, to enjoy cooler air overnight, where the humidity has been reduced. It has considerable benefits over other forms of ventilation


sep/oct 2023


like extractor fans and trickle vents, as well as passive stack, positive input or mechanical extract ventilation.


THE NEXT STEP However, a further step in the sustainability journey can be taken with the Heat Pump Ventilation (HPV) approach, such as combining HRV with an integral heat pump. It requires no gas connection, expensive oil, pellet storage space, ground-drilling, radiators or underoor heating. Heat is added to the fresh air supplied into habitable rooms of the house, via the ‘veins’ of the ventilation system – the ductwork, to provide highly energy efficient space heating. Multiple supply zones include


an individually controlled supply duct that utilises the cooler air before the heat pump gets involved, so the master bedroom could benefit from a lower temperature for example.


The beauty of this system is that in the summer months the heat pump can reverse automatically, to provide cooling and reduce humidity, so that a 4-5°C temperature reduction could be experienced. Not only is this economic, but it is healthy, as it doesn’t recycle air like an air-conditioner.


EXTRA HEAT Additionally, if a room-by-room heat- loss appraisal indicates more heat is required in certain rooms than others,


www.sbhonline.co.uk 63


How heat recovery ventilation works – here the unit is shown in a loft and is connected to ceiling terminals in each room by ducting, so you get a whole house air change every couple of hours without losing heat!


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