[Sbse] short, fat and straight

Dekay, R Mark mdekay at utk.edu
Wed May 26 21:46:22 PDT 2021

Hey Pal, Hi Jim,

I don’t understand the logic of your quest for the efficient organization of mechanically- provided fresh air.

To your point, No, actually, the air flow window can be in supply or exhaust mode, but in both cases provides heat exchange. Aalto did it in the 20s. A double envelope is a more crude / over-designed version of the intake air-flow window, if designed right. This is covered briefly in Sun, Wind & Light, 3rd Ed, in the AIR-FLOW WINDOWS strategy.  One could do the same with intake air channels in the wall—a circuitous path that picks up heat being lost through the envelope.

Both need an exhaust pressure source, either fan or stack.

I simply wonder why in a cold climate, one would use a ducted fresh air system in housing, which is very cellular spatially, not lending itself to air based systems beyond the apartment scale?

We are not talking about the space conditioning , right?

OK, you are on Wisconsin. it gets cold in winter, but the sun still shines. And you are designing a super-efficient passive house type envelope, SO, all you have to do is heat a small  amount of incoming fresh air. If you could use passive stack pressure to drive the system, plus an air-flow window to recover 50% of the  heat, then...... could you not use some passive solar direct gain (or other system type ) heat to make up the difference?

Alternatively, you could pre-heat the incoming air with free solar energy (transpired wall or air collector) and then use the air - flow window on the exhaust end to recover half the losses.

I end with a philosophical challenge: If the energy is free and on site, do you really care about ventilation air heat recovery efficiency?

Ok, maybe not the actual end...

Since the passive house envelope is so tight, you should need less passive solar aperture and less mass, compared to a Balcomb-era solar building. Therefore, you have huge excess potential for addressing the heat load of fresh air in the apartment itself, via passive solar gains, even without the heat recovery mentioned. Can’t we give up the machine?

Seeking an elegant diagram for the fit of spatial order to mechanical system order is only relevant if the complex centralized mechanical system is actually required. Once you have a passive solar heated high-performance passive house, why make the problem more complex simply for ventilation? It seems more interesting to ask, What elegant architectural order could provide fresh air free of machines and purchased energy?

And by extension, how could the daily interaction with such an ordered building engender rich occupant experiences? And in doing so, foster an awareness of nature’s daily and seasonal rhythms?


Mark DeKay, RA, Professor
School of Architecture
University of Tennessee

Sent from my iPad

On May 26, 2021, at 10:45 PM, James H Wasley <jwasley at uwm.edu> wrote:

Good to hear from you and all great ideas! These will go into another lecture on natural ventilation. Some thoughts to push back on, just to keep the conversation going:

  *   Everything you describe sounds like an 'exhaust only' ventilation strategy, which sacrifices heat recovery for simplicity... that's how my building works at least. But heat recovery seems critical for most net-zero case studies, at least in cold climates. True or false? (Yes, my world view is skewed towards solving for cold climates. Good point.)
  *   I'm vaguely familiar with the breathable wall idea. My young colleague Alex Timmer is obsessed with making walls work in this way- going so far as to trickle water through pervious concrete to make a passive cooling system. I'm terrified of the potential for IAQ problems.
  *   I used the Passive House apartment building as an example, but I'm looking for any large building where mechanical systems distribution and necessary ductwork have been rethought to minimize friction. Unlike the pump and pipe examples that Lovins' relies on, ductwork is BIG and has architectural impact.

Hope all is well with you,

James Wasley, AIA, LEED-AP

Professor, Department of Architecture

University of Wisconsin-Milwaukee

P.O. Box 413

Milwaukee, WI 53201-0413

phone- (414) 229-4045

cell- (414) 306-1242

From: Dekay, R Mark
Sent: Tuesday, May 25, 2021 10:46 AM
To: James H Wasley
Cc: Mailman - sbse at uidaho.edu
Subject: Re: [Sbse] short, fat and straight


In what climate?

How about….

  *   A no-duct building
  *   with all passive conditioning and if needed, radiant delivery.
  *   Passive fresh air ventilation is also possible. Think trickle vents and an atrium, for example.
  *   Or use air-flow windows (low-tech heat exchange) with stack-vent outlets. 50% efficient recovery. Stacks could be shared/ganged (like Eastgage Harare)
  *   Or one could use an air-flow wall (similar to air-flow windows) as intake
  *   Or the Danish/Swedish have worked on permeable wall systems with passive stack flow, where the whole wall is a low rate trickle system. I always though that had potential, but not sure if it got developed.
  *   Much of this suggests a two-level apartment. See variations in SWL3rd (Cross-ventilated rooms) to get stack and solve for corridors a the same time.


On May 24, 2021, at 10:16 PM, James H Wasley <jwasley at uwm.edu<mailto:jwasley at uwm.edu>> wrote:

Hi SBSE list serve,

Amory Lovins famously talks about reducing the energy use of air and water distribution systems by focusing design on reducing friction- producing pipe and duct runs that are short, fat and straight.

I'm looking for good case study buildings that illustrate this point. I'm hoping that they make the mechanical systems configuration an architectural question with a clear spatial logic- something that we see in the plan and section as distinctive and tied to net-zero as a goal.

The question that set off the hunt involved how one would do fresh air ventilation and heat recovery in a Passive House high rise... all options seem to be taken by different published buildings- an HRV in every unit, an HRV on every floor, and completely centralized systems. Given that I will never teach the detailed design of any of this equipment, I'm looking for buildings that plant the question provocatively and case studies that might illustrate how design teams have wrestled with this goal.

Much thanks, as always!

James Wasley, AIA, LEED-AP
Professor, Department of Architecture
University of Wisconsin-Milwaukee
P.O. Box 413
Milwaukee, WI 53201-0413
phone- (414) 229-4045
cell- (414) 306-1242

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