Can I install a MVHR system in a Victorian house?

Yes, you can! MVHR system installation in a Victorian house can even be DIY’d but there will be some challenges as this video explains.

SuperHomer Eric Fewster lives in a terraced house in Salford, Manchester. When he moved in to the house it was quite dark, dingy and damp, so part of the reason for refurbishing it was to resolve these issues.

He’d heard about Mechanical Ventilation with Heat Recovery (MVHR) and researched it on the internet and using books. The Energy Saving Trust website provided a lot of helpful information.

Installing MVHR for a whole house solution

Eric’s ‘whole house approach’ led him to fit a combination of internal wall insulation and MVHR. The goal was to get a very airtight well insulated house, preventing winter heat loss.

The external facing walls were insulated internally with 70mm of polyisocyanurate insulation board, friction fitted within a wooden studwork frame, with a vapour barrier and plasterboard on top. In a similar fashion, the suspended timber ground floor and bathroom roof were also insulated using 100mm and 120mm insulation respectively, while the loft was insulated with 270mm of mineral wool.

Benefits of MVHR with good levels of airtightness and insulation

Once you’ve got high levels of insulation and relative airtightness, MVHR gives you the controlled ventilation you need. Normally air would move freely between whatever openings you have between the house and the outside. You can, however, control the air flow by sealing up all those old air leaks, using mechanical ventilation instead. The advantage of MVHR is that it recovers heat from the stale warm damp air as you extract it from the house.

In Eric’s case, the MVHR unit in the loft recovers heat from the excess warm moist air that it draws from the cooking and washing areas, so you get heat coming back in the form of pre-heated fresh air. So, whilst it is extracting the stale air from the kitchen and bathroom, it is also bringing in fresh pre-warmed air to the lounge and bedrooms.

It is only because of mechanical ventilation that a draught-free, highly insulated house, with greatly reduced heating requirements is possible. For example, PassivHaus buildings, which require virtually no heating, do nonetheless require mechanical ventilation to ensure good air quality in winter.

For Eric an added benefit is that the air in his house now remains quite fresh and relative humidity is quite low, varying between 35 – 60% which is comfortable and not too damp.

Challenges when installing a MVHR system yourself

Eric fitted the MVHR unit himself with the help of someone else who also had no experience of domestic MVHR systems – this was mainly because it was difficult to find anyone with relevant expertise to fit it. He got a lot of satisfaction from doing the work himself and from ending up with a house that is very comfortable to live in, but there were some significant challenges:

1) Lack of instructions

The unit came as a kit with lots of fittings which didn’t fit into each other, no manual and no instructions. There was a manual on the internet but no readily accessible advice on how to fit it together.

2) Getting a tight seal on ducting
Leaks at joints on the air ducts were a problem. Joints had to be carefully taped, but even then seals were not sometimes adequate. For example, Eric had measured the temperature of the air coming from the bathroom and kitchen compared to air just prior to the heat exchange unit and found a significant temperature drop, which he attributed to cold air leaking in through a joint in the ductwork. As a result he both glued the joints and taped them again with the same foil-backed tape.

3) Concealing pipes between rooms

Some of the pipes to the unit were also hard to fit. For example, the pipe from the kitchen via the bathroom had to go through the floorboards of the bathroom, out into the hallway and up the side of the wall up into the loft. A combination of circular and rectangular fittings were needed and a frame that could then be plasterboarded to disguise it.

Blower test following MVHR installation

When the work on the house was almost finished a blower door test was undertaken to find out how leaky the house was. This highlighted  some significant remaining gaps in the building envelope that Eric plugged after the test.

Find out more – visit a refurbished home

You can find out more about MVHR at green open house events in September. Speak to real homeowners as they share their personal experience of refurbishing their homes as part of SuperHome Open Days. SuperHomes are older homes refurbished by their owners for greater comfort, lower bills and far fewer carbon emissions – at least 60% less! Entry is free. Book now.

Also See:
Green your home’s building fabric
Draught-proofing- a good thing?
Insulating a solid wall

Visit a house with MVHR in Sep 2016
You can see MVHR at 25 open home events around the UK this month. See our events listing for details and simply filter for ‘mechanical ventilation heat recovery’. SuperHome tours and Q&A sessions will let you quiz the owners, so you can discover what worked and get frank feedback on anything that didn’t. Entry is free.  SuperHomes are older homes refurbished by their owners for much greater comfort, lower bills and far lower carbon emissions – at least 60% lower! This makes them a great source of ideas to help you green your own home.

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