HVAC LEED Contributions

[cry22]

I wonder, how much energy savings over ASHRAE 90.1 you guys are getting for office buildings in mderate climates?
In very cold climates we've been able to document as much as 58%.
Are you down sizing your chiller and boiler plants as a result of LEED? Do you remove some conservatism from your design because of LEED?

We have been able to get as much as 550 SF/ton for office buildings with Low-E glass and total energy recovery.

When we take away the descicant wheels, we have a hard time meeting the typcal mandate of ASHRAE 90.1 + 20%.

What is your experience and what are the LEED features you are implementing?

The following are the classics LEED features we implement:

1. Total energy wheels.
2. Air side economizers.
3. High efficiency condensing boilers.
4. Low-E glass, U=0.4, SC=0.3
5. DDC controls.
6. Low electrical loads (1 watt per SF for lighting)
7. 0.5 watts per SF for equipment.
8. dedicated 24-hour cooling systems (DX, dry coolers, etc) to shut down the chiller plant.
9. CO2 sensors for demand controlled ventilation.

The non-classics:

1. Geothermal energy.
2. Dynamic air filters, reducing static pressures by 1" on typical VAV systems.

What water saving features are you using? Have you implemented teh Dolphin water treatment system in lieu fo chemical treatment for cooling towers?

Hope to generate some contributions for all.

 

[GMcD]

All of the above, and continual beating up the architects to get better window to opaque wall ratios and higher performance glass, as well as better envelope detailing to eliminate thermal bridging. The key is for the mech engineer and elec engineer to get together to show the cost savings in the mech and elec central equipment /plant and infrastructure costs to pay for the high performance envelope so the total building budget is the same, or less than a conventional "to code" building. External sun-shades are another big energy saver that has very low life cycle cost - fixed, just needs some cleaning every now and then, and there for the life of the building blocking those pesky perimeter transient solar gains.

In milder climates it also pays to look at low temperature heating water and high temperature chilled water. In the Pacific NW I am using 55F CHW supply temps and 100F heating water temps and using combinations of radiant heating/cooling, and demand controlled DOAS and we are seeing 60%-70% below ASHRAE 90.1-2004 as budget compliant potential systems. In climate zones where de-humidification is needed, then the dessicant energy recovery systems come into play and combinations of low and high temperature chilled water circuits can work.

 

[ChrisConley]

We use most/all of the above and in addition strap a VFD onto almost any motor we can find (within reason of course). CO2 sensors for ventilation control, displacement ventilation where appropriate.

Solar domestic hot water heating is becoming a standard now that there are a number of grants in place. Plus I like adding solar panels to a 'green' building, most green upgrades are invisible. Many of our clients like the solar panels because they are visible.

We've also done some daylight harvesting/occupancy sensor work on the lighting: dimmable ballasts, etc.

We tend to focus on low and ultra-low consumption plumbing fixtures for water consumption. We've developed some grey water / rainwater harvesting for irrigation as well. I've specified the ultrasonic cooling tower cleaning system, but not for water conservation.

Geothermal is a difficult one in our climate, we've used it but just for very specific applications.

 

[GMcD]

Rainwater harvesting is a good one in the Pacific NW, the challenge is finding economic practical storage for the rain water. These:

http://www.brentwoodindustries.com/water/stormwater.html

have been looking good in my area - all recycled plastic, and reasonable cost to install in a buried tank configuration. Use the rainwater for any cooling tower make-up and greywater toilet flushing service.

In climates where cooler seasonal temperatures are common, we are using a free cooling dry cooler to make 55F chilled water for server rooms, comm rooms and other 24/7 cooling applications to generate chilled water during the fall/winter/spring to avoid refrigerant based split systems and running chillers at low loads.

 

[cry22]

GMcD
Have you used the harvested water for cooling tower make-up? any special filtration?
I also see some places with high wet bulbs (Dubai mainly-wet bulbs as high as 85F) collecting condensate for cooling tower make-up (no need for filtration there).
DOAS systems, wonder how you model that in a program such as Trace for LCC to document the savings. any thoughts?

I've had some chances to implement co-gen for a large prison but was rejected by higher ups, the idea died somewhere along the way, although I though a very viable solution. EPA emissions restrictions have been a big obstacle for Co-Gen in the US. Wonder what the practice is around the world for Co-Gen.

Thanks all, keep pitching.

 

[GMcD]

Don't get me going about Dubai- the most unsustainable un-green blot on the planet, right up there with Ft. McMurray, Alberta.

Harvested rainwater does need basic filtration, just a glorified pool filter or cartridge filter set with good debris settling interceptor upstream of the cistern for irrigation and Tower make-up water purposes and other non-potable water applications. The biggest barrier has been the Building Code here- "all plumbing fixtures must be connected to potable water" - which means "drinking water quality" and then you're into some more expensive water treatment, just to flush a toilet....

Cogen still uses fossil fuel- the whole point is to try to design in as much passive building envelope "systems" as possible to reduce the overall gross energy required to provide indoor comfort and lighting before "active" systems need to be applied. The Mechanical Engineer needs to learn to speak "architect", and get involved with the basic building envelope design as early as possible in the game. You wouldn't believe the aesthetic resistance to exterior fixed sunshades, but when the mechanical engineer does a quick economic study of the cost savings in cooling plant size and operating costs vs the cost of the sunshades, the Owner is usually glaring at the Architect asking "why not??" Don't forget the added glare control and enhanced IEQ due to cutting off direct solar glare from perimeter offices so people can actually see their computer screens again - no $$ that can be captured there, but certainly a tangible, measurable issue.

Trace, HAP, DOE-2, etc. are all "air temperature based" programs and cannot model radiant heating/cooling very well, if at all. DOAS with demand ventilation can be modeled on those programs by assigning arbitrary schedules to the fan on/off or speed/volume settings. Unless you have some way of programming in CO2 level variations based on occupancy.....

The Life Cycle Costs are still done by hand and it's really only a guesstimate - the volatile cost of energy, with regional and seasonal variations in equipment and systems costs vary too much to provide any more than a good estimate. Passive systems obviously have the lowest life cycle cost - needs little maintenance, no moving parts, and lasts the life of the building.

 

[ozmosis]

Don't forget one important issue:
getting the right people with the right skills to put the right products together. USGB sort of touches on it but the right products in the wrong hands will not save energy, the wrong products in the right hands will be better and..well, you know what comes next.