Can I install a MVHR system in a Victorian house?

Yes, you can! DIY installation of MVHR is possible in a Victorian house, although 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 and 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 insulation board, friction fitted within a wooden stud work frame, with a vapour barrier and plaster board on top.
Benefits of MVHR with internal wall insulation
MVHR combined with internal wall insulation is a way to deal with draughts in a house. Normally air would move freely between whatever openings you have between the house and the outside. You can control the air flow by sealing up all those old leaks and using mechanical ventilation. MVHR recovers heat from the stale warm damp air you no longer want 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. 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. 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 MVHR yourself:
Eric fitted the MVHR unit himself mainly because it was difficult to find anyone to fit it with him. 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 little 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 piping

Leaks on the piping were a problem, particular due to dust. Eric measured the temperature of the air coming from the bathroom and kitchen to the unit and there was some air loss in the pipe in the loft because air was leaking in through a join in the pipework. As a result he 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 plaster boarded 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 showed some significant gaps still in the building envelope that Eric plugged after the test.
SuperHome status
SuperHome status
This house is one of the homes in the SuperHomes network of older homes that have been renovated by their owners to reduce carbon emissions by at least 60%. Most SuperHomes host public open days in spring or September. For more, visit Eric's SuperHome.

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