Sunday, 16 October 2016

Re -Think of Ventilation.

As detailed in my previous post the current solution built into the house to provide passive north facing ventilation is not fit for purpose. The current design is the sort of system that is usually installed into basements to provide ventilation and a little light.

In our case the restriction, imposed by the planning authority, on the height of the vent chambers that form an integral part of the roof structure significantly affected the design and execution options.

However if one stands back and accepts that the current solution does not work, what is really required is a means to readily remove the accumulated hot stale air. A series of venting chimneys with spinning wind driven cowls, to draw out the hot air, could probably achieve this.

Taking this one step further by designing chimneys and cowls to not only remove the stale air, but also introduce fresh air would be a marked improvement. The Bed Zed ventilation cowls (see below) have been used widely to achieve this in several major building projects. The schematic below illustrates how, by using a rotating collar, the wind vane aligns the cowls so that the stale air is removed and the fresh air is taken into the house.

These units are quite large, would need to be fabricated locally and be in keeping with the neo-brutalism design of the house.

A short search on the internet for "passive ventilation" revealed a range of products made by the Ventive company in the UK. Although these are more sophisticated than I really require, since they include heat exchangers to help in maintaining the inside house temperatures when introducing fresh air. They do, however, offer simple profiles and there are options for installing in chimneys. This is a vital factor in our case, since, the height restriction applied to the vent chambers as an integral part of the structure, does not appear to apply to chimneys!!

Retrofitting such solutions into the house requires further research and discussions with Ventive but on the face of it does seem to offer a possible solution to the problem.

Bed Zed ventilation cowls. Photo courtesy of

Schematic of a Bed Zed cowl. Courtesy of "The Green Building Bible Volume 2"

An angular version of the above.

Ventive passive ventilation fitted to standard chimney flues. Photo courtesy of

Schematic of Ventive C-900 system. Courtesy