Thursday, December 16, 2010

ASHRAE 170 & Air Curtains

We recently became involved in a discussion with an engineer who questioned whether or not ASHRAE 170 allows for the use of air curtains. His question was prompted by misinformation from a manufacturer who, incidentally, does not make air curtains.

The purpose of 170 is to establish a minimum standard for designers and engineers of healthcare facilities. 170 is not intended to recommend or exclude a manufacturer, particular product, or even a particular way of doing things. Engineers can choose to exceed this standard if they so wish. Anyone’s assertions to the contrary is nonsense.

We applaud the work of the 170 committee since such a standard has been long absent in our industry. Not unexpectedly, the establishment of ASHRAE 170 has raised awareness of the critical nature of the operating room. For Krueger, sales of air curtain systems have risen as a result. (The effectiveness of air curtains, and particularly Krueger’s Sterilflo System, is well established. The ASHRAE whitepaper DA-07-037, as well as the article regarding air curtains in the March issue of the ASHRAE Journal review their history, their functional parameters, and the microbiologic cleanliness that can be achieved.)

If this manufacturer truly believes that ASHRAE 170 precludes air curtains, the proper response is to ask for an interpretation regarding this issue by the SSPC, using published ASHRAE processes, not to engage in misinformation.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, November 29, 2010

Greenbuild Summary

I spent three days in Chicago at the Greenbuild convention. It was reported that it was the largest ever.

The big HVAC product seems to be Chilled Beams. There were at least seven (likely more) booths with Ceiling Chilled Beams and a few with Displacement Ventilation. Some booths even had regular overhead diffusers. Mostly though, it was Green construction and Green building material displays. Many of the attendees seemed to be Green consultants.

During my visit, I spent a couple hours in the USGBC “Knowledge Booth”. I enjoyed many of the conversations and discussions, but one topic that came up repeatedly was about Underfloor (UFAD) Technology. It appears there are still a number of misconceptions. To achieve a well working system and minimize complications, planning a UFAD project from the ground up is the most important step.

Authored by: Dan Int-Hout, Chief Engineer Krueger

AHRI Meeting in Phoenix

I participated in the semi annual AHRI meeting, held in Phoenix this year. A number of changes were approved for VAV box certification and data collection, which will be implemented over the next couple of years. These changes include the following:

1.) Certified data will be embedded in application data (in addition to a separate table of just certified data). This will require most manufacturers to reformat the appearance of application data, but not change any data. This is to be implemented immediately in electronic data, and eventually in reprints of catalog data. Krueger has already accomplished most of these changes in our online data.

2.) The method of test for sound power is being changed for discharge sound to include “end reflection” in the reverb room. This has been apart of other methods for reverb sound for other products, but never included in VAV box testing until now. This change will slightly increase the sound power levels to discharge sound in low frequencies, and will likely result in a minor increase to the reported discharge NC level. The effect will be greatest for small units (where discharge sound is seldom critical). This move is to put the AHRI 880 test method in line with other test methods. The proposed timeline is to have electronic data available within one year, and printed catalogs within three years. All new data shall be end reflection corrected. New data will be identified as tested per AHRI 880-2011. Krueger has already initiated these data recalculations and will have the on-line data posted in mid 2011.

3.) VVT type dampers are now going to be certified as single duct VAV boxes. They have been exempt in the past.

4.) ASHRAE 90.1 has requested that we report casing and damper leakage as a part of our certification program. This is currently being developed.

The next meeting of AHRI will be in the spring of 2011.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Monday, November 8, 2010

Net Zero Acceptable Buildings

ASHRAE and the USGBC have adapted the slogan “Net Zero Energy Buildings” as the goal for building design. This is of course an admirable goal. Energy efficiency is a worthwhile, and likely a critical strategic goal. It is important, however, to put everything in a proper perspective. In commercial buildings, which are a significant percentage of our building energy use, energy costs are insignificant compared to building salaries. Saving energy at the expense of building occupant productivity is a “zero-net-sum” solution. BOMA has stated that the highest reason given for not renewing the lease has been “occupant dissatisfaction with the environment”.

The function of buildings is to provide a suitable environment for the occupants of said buildings. The average occupant salary in commercial office buildings has been estimated at between $200 and $300 per square foot per year of office space. Total building energy costs are on the order of $2 to $3 per square foot per year. If we could actually achieve a Net Zero building, it would account for a savings of 1% of the total. 

All too often the occupant expenses are missing in the analysis of real building costs. Most important in determining the cost of occupancy is the issue of occupant productivity, as that is where the real costs (and savings) are realized. A number of factors affect productivity, but occupant satisfaction with the thermal environment is one of the most significant ones. 

In attempts to reduce energy by using different systems, there is an opportunity to overlook the occupant satisfaction in the resulting environment. In fact, sometimes there is a negotiated tradeoff between energy and system comfort. I assume they did not consult the occupants in these negotiations. It is proposed for LEED 2012 that a comprehensive occupant survey be a mandatory requirement. A building which is unacceptable to the occupants should be considered a design failure, no matter how much or how little energy it uses.

Unfortunately, improperly selected, designed, and installed air delivery systems often result in excessive stratification, even though it is clear how to avoid this at the design stage. When systems are overly stratified, feet are cold, ventilation mixing is likely compromised, and thermostat response can be orders of magnitude slower than with properly mixed systems. 

Proper selection of the air delivery system for a building can assure occupant satisfaction, assuming the design follows known and accepted guidelines. Ignoring these rules however can result in drafty uncomfortable spaces.

Saving energy is an admirable goal, but we need to assess, and include, the real cost of productivity. Failure to do so guarantees that what will be achieved is a Net Zero Acceptable Building.

* For more information on this topic, please see an upcoming article written by Dan Int-Hout for ASHRAE Journal.  

Authored by: Dan Int-Hout, Chief Engineer Krueger