Heat recovery is difficult to implement in passive stack ventilation because the pressure loss is usually too high in conventional heat exchangers compared with the stack pressure. Laboratory investigation and computer simulation have been carried out on a low pressure-loss heat recovery device based on heat pipes which is suitable for application in passive stack systems and other systems where a low pressure loss is essential. It was found that heat recovery efficiency decreased with increasing air velocity.

In order to understand why Mechanical Ventilation with Heat Recovery is common in some countries of Europe yet installed in a small minority of domestic dwellings in the UK, surveys of Regional Electricity Companies and distributors have been carried out to identify whether there are grants available to promote the system in the UK and what influences sales of the system across Europe. A review of other heat recovery systems is provided to assess whether they are competitiors.

The requirements to know indoor thermal comfort ask for a more detailed study of room temperature responses. Although CFO (Computational Fluid Dynamics) techniques can be applied successfully to the prediction of indoor temperature distributions, using them for the dynamic calculation of temperatures and air flows is still a very expensive expenditure. For indoor climate control systems, it is necessary to make quick calculations of the dynamic temperature distributions in a room.

To control the indoor thermal environment within the comfortable range, the dynamic temperature distributions and flows of room air must be correctly predicted. While the CFO (Computational Fluid Dynamics) technique can be used to carry out such a prediction task, its drawback is also obvious: too time-consuming. To solve this problem, the dynamic temperature distributions can be predicted with some fixed air flow fields calculated with CFD codes. That is, sacrifice the dynamics of indoor air flows and only preserve the dynamics of the temperature distributions.

In the frame work of IBA Task XIII, a pilot project URBAN VILLA has been realized in Amstelveen, The Netherlands, Ref. /1/. This project concerns the development of an apartment building of 42 luxurious apartments, of which 16 will have extreme low energy consumption. Success and failure of every new domestic design are ruled by the sensation of comfort, experienced by the residents. Therefore, in order to make this a successful project comfort requirements should be fulfilled.

 Calibrating air flow measurement devices is a constant headache for users in the field. Peter Downing explains how sophisticated ultrasonics can overcome the problem.            

A study comparing the effectiveness (as reported by occupants) of passive stack ventilation (PSY) and mechanical extract fans (MEFs) was carried out during the winter of 1996. This involved a face-to-face survey of 437 homes in England. More than 50% of the homes in the study had MEFs, 14% had PSV and 8% had humidistat-controlled MEFs (HMEFs). About 25% of the homes had either a kitchen or a bathroom with no ventilation device and 16% had no ventilation device in the home.