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 hollow core concrete slab cavities are open on wind side of building, other half open to leeward side. Openings are provided between cavities and ventilated space at opposite side of facade 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 issue with lost fire rating between building floors due to penetrations
  • Could work in warm as well as cold climates 
Disadvantages are:
  • Cocurrent heat exchange = lower heat recovery effeciency
  • Dependence on wind means larger fluctuations in flow
Final reflections:
  • Flow could be controlled by casting in 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