Tuesday, September 25, 2012

The Energy Code Challenge

ASHRAE Standard 90.1 2010 will be “strongly suggested” to be adopted in codes next year. (October 18 2013 is the date mandated by the US D.O.E.) ASHRAE 189 2010 will push the envelope further, and will be code in a few locations. This revision to the 90.1 Standard, as well as the new 189 Standard, will impact the way we design systems. Just recently, I attended a seminar outlining the impact of the updated standards. 52 of the 110 changes to the 2010 revision affect HVAC systems. 25K sq ft, single zone, 2 floors or less, and constant volume is a lower limit on simple systems. The Performance Rating Method, appendix G, is not mandatory, but is used for LEED comparison purposes. The Standard provides both a “Prescriptive” and a “Performance” path. This allows some flexibility in selecting the design. Air cooled equipment will be harder and harder to comply with the Standard. Water cooled equipment makes lots of alternate systems practical, including using water to move and remove heat.

Some of the issues, and how they may affect us in the air distribution wing of the HVAC industry, are as follows:

Rooftop units: Chilled Water with 5hp fans or DX > 9 tons must vary the airflow rate at low loads, which means a variable minimum outside air flow rate. Dynamic Ventilation rate control is also required.

Economizer: Previously, economizer was mandated only in milder climates, but now it has “Moved South”. Smaller rooftop units must have this capability. This will make rooftop units more complex (and expensive). It may push for VAV in many spaces that were constant volume in the past.

Reheat: Restrictions will cause engineers to rethink how they control humidity. I suspect fan powered terminal units will continue to replace single duct / reheat units as the rules tighten up.

Energy Recovery (Time for suppliers to dance a jig!): Energy recovery will become a major component of any outside air treatment system. I suspect DOAS (Dedicated Outdoor Air Systems) will get a huge boost with this.

Other requirements: Half the electrical outlets will be shut off during unoccupied periods. Roofs must reflect heat. Interior lights must be reduced. Most importantly, appendix G (which defines ‘baseline systems’) is being modified, which affects the push towards implementation of new systems.

Duct Leakage is emphasized as a major energy waster, and the new standard has very tough rules.

Finally, perimeter envelopes are highly regulated. This is especially good news as the perimeter is where most of a modern building’s energy is being consumed.

The result of all these changes will be to further reduce the energy use in the interior of buildings. This reinforces the idea that the ventilation rate requirement is the load in the interior. As perimeters get better, the ventilation rate will drive them as well. All HVAC system strategies, be they VRV, WSHP, UV, Fan Coil, DV or any other method, all require ventilation air, which is becoming the major component of the load calculations. We will come to realize that these ventilation systems need to be pressure independent as ventilation demands change within a space. In other words, VAV systems will continue to be a part of ANY HVAC system.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Wednesday, September 19, 2012

My Findings in Washington D.C

I spent the last few days in our nation’s capitol. In the schedule were a couple of speaking engagements as well as a few sales calls with our Terminal Unit Product Manager.

Interestingly, Washington D.C. has a number of very “progressive” Mechanical Engineering firms – probably more than any other city I have visited. All are very interested in “pushing the envelope” in air distribution designs and are, in one way or another, using a series fan powered VAV terminal unit as the basis of their designs, always with an ECM motor. Most are using a “Chilled Box”, or DOAS fan terminal unit, as it is sometimes called, which is a series fan box with a sensible cooling coil on the induction port. We have a white paper on this technology on the Krueger website. (http://www.krueger-hvac.com/lit/pdf/DOAS_Fan_Powered_Terminal_Unit.pdf).

The DOAS terminal unit was the subject of the Washington D.C. chapter ASHRAE dinner talk, presented by Southland Industries. They recently finished a retrofit of the Pentagon using this technology. The talk was an excellent discussion of both the development of this strategy and the control options possible. They mentioned the beginnings of the concept and even the SSA Payment Centers with which I was involved in the ‘70’s, a precursor to this concept. My first exposure to the concept dates back to 1991. Similar to Carrier’s 36 series induction units, first installed in 1948, both the chilled beam and the DOAS fan terminal units use similar technology by combining non-condensating cooling coils and conditioned primary air to handle the sensible load in the space. That product was one of the many products I supported as terminal engineering manager back then. It is gratifying to see the excitement we observed on this technology at the many engineering firms we deal with in the D.C. area. In fact, one participant during the Q&A period stated “Since this is obviously the way we are going to be doing things in the future.”

I couldn’t agree more. The use of variable flow ECM motor technology, tied to a sensible cooling coil and a low temperature DOAS system, will likely be the most cost effective way to provide load management and ventilation to many types of spaces for some time to come.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Thursday, September 6, 2012

More on the Cost of Cool

Last week I posted some numbers from an article in the New York Times on the true cost and future of air conditioning. I have since received some interesting data on the reported energy use of some Government buildings. What I received was this:

Here are some facts to describe government building energy performance compared with the private sector. The latest CBECS Table E2A says the average energy consumption for all buildings is 91,000 Btu/SF/Yr. The 2007 Federal Government measured building energy data is:

Agency - BTU/GSF
EPA - 315,867
HHS - 313,512
DOJ - 239,558
DOE - 230,194
GSA - 74,512
Government Total - 117,495

It would appear that the GSA is doing a good job of saving energy, at least compared to the average. The same cannot be said of the other agencies. Assuming the data is accurate, the DOE, who is behind the Energy Star Programs, apparently hasn’t used their own recommendations. I attempted to break this down into average costs, but it appears it is incredibly dependent on location.

What has become apparent, however, is that interior loads continue to drop, and the main difference between different building’s energy costs is likely the envelope efficiency. Changing the thermostat setting will likely have a net zero cost on energy use, because interior loads are pretty much independent of climate, but building a better building skin is where the real savings are. Trying to squeeze energy out of interior HVAC system components is likely a fool’s errand. Energy used in the interior is converted to heat and must be removed, no matter what the setpoint, and to a great extent, no matter how it is removed. True and meaningful energy savings can be achieved by treating outside / ventilation air and avoiding over-cooling spaces when controlling humidity. Furthermore, we are realizing that the minimum ventilation rate is actually the load in interior spaces.

In summary, let’s speak to the architects about making buildings energy efficient instead of trying to squeeze the last drop of savings out of HVAC systems.

Authored by: Dan Int-Hout, Chief Engineer Krueger