Cross Ventilation Heat Recovery Concept

Since this blog is still getting traffic (from what I naively hope is relevant industry people, not bots), I thought I would share another ventilation concept that is similar to the StackHR concept in that it utilizes hollow core slabs and provides heat recovery and preheating of the ventilation air. All credit for the idea goes to my dad who came up with the concept when I pitched the original StackHR concept for him.

I have sketched the concept below:

If it isn’t completely clear what’s going on from the sketch here comes an explanation:
Half of the hollow core concrete slab cavities are open to the windward side of building, other half are open to leeward side. Openings are provided between the cavities and the ventilated space opposite of  thefacade opening.
Air enters building on windward side, passes through slab, enters ventilates space on leeward side, passes through ventilated space, exits ventilated space on windward side, passes through slab, exits building on leeward side.

Advantages over the original StackHR concept are:

  • No minimum number of building floors for system to work
  • Higher driving pressure
  • No potential issue with lost fire rating between building floors due to penetrations between floors
  • Could work in warm as well as cold climates 
Disadvantages are:
  • Co-current heat exchange = lower heat recovery efficiency
  • Dependence on wind means larger fluctuations in flow
Final reflections:
  • Flow could be controlled with automatic dampers similar to Lindab’s DAU dampers
  • Heat exchange could be made to take place in each cavity as with the original StackHR concept to increase heat recovery efficiency, but due to the lower theoretical maximum efficiency it is likely better to go with the simpler design illustrated above