Ventilation is a big issue these days. We need good clean air to live. As you may have noted from elsewhere in this project blog, the need to manage humidity and condensation in a timber framed building is of great significance. This, above most other things, has been a guiding principle impacting most design decisions on the refurbishment project. The installation of an efficient mechanical ventilation and heat recovery (MVHR) system was anticipated at day one and carefully integrating such a system into the cottage was always going to require forethought and care.

Such systems are common place now in modern new-builds. Less so in refurbishments where retro-fitting is more complex. We opted to make use of the highly efficient Vent-Axia MVHR system supplied by BPC Ventilation

The system is simple. Fresh air is drawn in from outside and passed to the internal living rooms of the cottage, but only after it is pre-heated by exchanging heat from warm moist air drawn from the bathrooms, WCs and kitchen spaces. The extracted waste air is then exhausted to the atmosphere. The system is said to be over 90% efficient.

Our system was supplied as a ready to install kit. However, given the constraints imposed by the building’s listed structure, we needed to find ways of installing the MVHR unit, plenums and the ducting without compromising the historic fabric. The MVHR unit is sited in the small loft space above the bathrooms. This makes for easy access to the eves for the supply and extract air ducts. The MVHR unit air filters can also be accessed ready for regular cleaning and maintenance.

The supply and extract ducts radiate from a pair of stainless steel manifolds, the number of supply and extract ducts matching as far as possible to enable a “balanced” system. Whist this would be especially important in the case of a fully sealed “passive house”, it is good practice in this case notwithstanding the inevitably “leaky” nature of this historic building refurbishment. The real benefit will be minimising the potential for humidity and condensation build-up without the sacrifice of heat loss, particularly during the winter months.

The challenge of threading up to 15m of ducting to the various extremities of the cottage was overcome by making use of one of the four chimney flues that extend through the full height of the building. Three ducts were dropped down the flue through a small aperture in the loft side of the stack. The flue used to serve the lower ground floor fireplace at the bottom of the building, so it provides a ready and direct route for supply air to the most distant parts of the building.

One day soon we’ll be switching the system on for the first time, so hopefully it works as I intended!

The porch takes shape

The metal structure with its cantilever roof has now been measured by the glass fabricators in anticipation of the glazing being installed. This was to have been in around twelve weeks time. Not now I’m afraid. Like everyone else, we’ve been struck by the global Covid-19 virus pandemic and this has hit our supply chain.

Prior to the pandemic hitting we did manage to get the porch’s timber structure and insulated warm-deck roof formed, ready for cladding and finishing when conditions allow. The roof-light aperture and the extent of glazing is now apparent and the roof structure appears to magically float, completely unsupported adjacent to the cottage – it’s going to look fabulous!

Work is still progressing slowly on the interior. Steve and Healey are continuing to work for the sake of their own livelihoods, at least until such time as authority dictates otherwise. Strict social distancing measures, however, require that I cannot be on site, which is an enormous frustration. In the circumstances I’m going to use this time of enforced isolation from the cottage to try and bring this blog up to date and provide further details of what was happening prior to the pandemic hitting.