Heat Recovery Ventilation
Mechanical Ventilation with Heat Recovery (MVHR)
It's important for your property to breathe, especially when it's super insulated and airtight to provide maximum energy efficiency. But if 'breathing' means dumping all your warm air only to replace it with cold air just to remove moisture, dust and odours, there has to be a better more efficient way to ventilate a building?
Welcome to Mechanical Ventilation with Heat Recovery (MVHR). A balanced ventilation system that both supplies and extracts air, providing fresh filtered air 24x7 with negligible heat loss. On this page you can find out how an MVHR works, see a simple MVHR diagram, understand the drawbacks of extract-only ventilation and learn about the benefits of radial ducting compared to branch ducting. We can even show you heat recovery evidence and estimated MVHR running costs.
Solarcrest specialise in the self-build, retrofit and refurbishment markets. We're happy to work with self installers and builders who are new to MVHR, providing technical support and advice through the install. Alternatively we'll fit the whole system for you. Either way Solarcrest offer a commissioning service to ensure your system is set up correctly and compliant with building regulations.
* Building regulations require one air change every two hours (0.5 ACH). With traditional extract-only ventilation that means your boiler has to warm up a house full of cold air 12 times a day.
How an MVHR works..
Typically 20%-30% of your space heating energy is lost through 'natural' ventilation; trickle vents in windows, extractor fans in wet rooms, and gaps in the building fabric. Rather than dumping warm air out of the building in the name of ventilation, an MVHR draws stale moist air from kitchens, bathrooms and utility rooms into a heat exchanger. At the same time another fan in the MVHR draws fresh air from outside which is filtered then gently fed into into bedrooms and living spaces. In a well insulated building the heat exchanger transfers around 90% of the heat from the old air to the new, so if the temperature of the stale air leaving the bathroom is 20C the temperature of the fresh air supplied to the living rooms is around 18C. You boiler just needs to top this back up to 20C rather than warming up a whole house full of cold (unfiltered) air. An MVHR therefore reduces your heating bills and improves your air quality. Dry air also costs less to heat than moist air.
As spiraling energy costs start to exceed mortgage repayments the need to conserve heat and power becomes increasingly important. To really cut the costs your house needs to become airtight. Ventilating an airtight house by fitting vents (holes) in the window frames and sucking warm air out of wet rooms defeats the object, so the only way to ventilate an efficient home is a balanced (supply/extract) whole house MVHR system. At least that's our opinion and the Energy Saving Trust seem to agree.
How 'green' are MVHR's?
What's up with extract ventilation?
A balanced MVHR system gently supplys air to dry rooms to create a positive air pressure, at the same time extracting the same amount of air from wet rooms to create a low pressure. As the air pressure equalises the flow of air is 'mechanically' controlled from bedrooms towards bathrooms before being removed from the property. Tradition extract-only ventilation on the other hand only removes air and so lowers the pressure in the wet rooms. The air it removes has to be replaced, so trickle vents are fitted on window frames to create an air path that allows fresh air in. There are three problems with extract-only ventilation: