Wednesday, November 4, 2015

CO2 is a problem?

I recently received a link to a new paper on the effect of elevated levels of CO2 on the cognitive ability of building occupants. This explains why student test scores are reported to be higher as ventilation rates increase. While LEED gives a point for increasing ventilation 30% above the 62.1 minimums, the implication here is that the ventilation rate needs to be quite a bit higher than that.

http://thinkprogress.org/climate/2015/10/26/3714853/carbon-dioxide-impair-brain/?utm_source=newsletter&utm_medium=email&utm_campaign=tptop3&utm_term=5&utm_content=5

Currently, outdoor CO2 levels are approaching 400ppm. The report states that while no ‘critical’ level is defined for indoor spaces, the 62.1 DCV (Demand Controlled Ventilation) suggests that it be “700 ppm above outside”, or no more than 1100 ppm total, which is quite a bit higher than what is found to be “safe”. They seem to believe that 600ppm is a good target.

Achieving this will require an efficient means of introducing outside air into a building.

One option is to simply increase the outdoor air setting of the air handler, but most units are designed to handle only about 30% of the unit’s air flow capacity for the climate in which it is installed, so this may not provide enough ventilation. Another option is to increase the percentage of outside air, but that would likely generate limitations with regard to dehumidification capacity and temperature. I believe the most effective method of introducing ventilation is to vary the quantity of ventilation air to the spaces that need it, which would imply the use of a Dedicated Outdoor Air System, or DOAS.

For this concept to work properly, the DOAS unit would likely need to be at a little larger than typical. It would also require an effective delivery system. For it to be energy efficient, it must only deliver as much outside air to each space as is required, which would involve a measured and controlled air flow damper at each zone. The VAV DOAS unit would then supply dry, cool ventilation. Doing this however comes with the risk of sub cooling spaces if the dehumidified ventilation air is not reheated (resulting from minimum ventilation rates that exceed the load). 

I’m sure there are other possible means of accomplishing this, but it’s likely that they would not be quite as cost effective as the DOAS solution. 

At Krueger, we call our DOAS unit a “Chilled Box”, which is an ECM variable speed, series flow, fan-powered terminal unit with a sensible cooling coil on the induction inlet. I encourage you to read my recent ASHRAE Journal article on this topic, as it not only provides a solution to address this CO2 issue, but it can also satisfy a number of other ventilation challenges you may come across.

Friday, October 2, 2015

Underfloor Products

With installations taking place in millions of square feet of office space, underfloor air distribution (UFAD) is seemingly gaining in popularity, at least when compared to where it was just a few years ago. In fact, Krueger just recently released their new and improved line of UFAD products that include interior, perimeter, partially stratified, and true displacement ventilation solutions.

As chair of the Technical Committee for the rewriting of ASHRAE’s UFAD design guide, I became much more familiar with the details surrounding underfloor air distribution, both good and bad.

- It provides a truly flexible solution and is great for high-churn applications.

- It allows users to be in more control of their comfort by way of controlling the flow of air in their immediate space.

- It requires careful coordination with all the construction trades to avoid the loss of conditioned air into unwanted spaces (leakage).

- Designs must take into account the perimeter to properly handle solar loads. (This can be said for any form of air distribution!)

- There must be controls in place to maintain humidity control. Should moisture issues arise, they may not be apparent until it has caused a more severe problem.

Luckily though, with proper planning and when you can find the right partners and product mix, all these details can be addressed to ensure a successful UFAD system. (Of course, with the products come the expertise and guidance from the supplier - like Krueger, who has installed many successful UFAD projects.) So, if you haven’t already, take another look at UFAD, it’s a proven technology that can offer many benefits to building owners and occupants.

Learn about Krueger’s new line of underfloor products.
https://www.krueger-hvac.com/Catalog%20Home/Underfloor

Friday, February 6, 2015

Top Ten HVAC Predictions Scores for 2014

Now that a certain event has past (weekend before last) I can finally score myself on my predictions for last year.

1. LEED V4, released last fall, includes a reference to either AHRI 885 or the ASHRAE Handbooks to prove compliance to acoustical requirements. The handbooks are missing a critical path table for the sound transmitted from a plenum noise source into a space. The incoming chair of TC 2.1 has indicated he will get the missing ceiling table included in the Handbooks. I predict he will fail in this effort for at least three years and that the 885 handbooks will be the only easy path to compliance. (One can hire an acoustician, of course, and TC 2.6 is populated with them). Yup. Nothing happening - 10 points.

2. Installed linear diffusers will still fail to have pattern controllers set prior to balancing. If adjusted after balancing, rebalancing is required. It is the design engineer’s responsibility to provide the adjustment information. The installing contractor should be designated as the one responsible for setting the pattern deflectors. I saw close to 1000 Engineers last year. Only a couple admitted it was their responsibility to specify who was to adjust them and to provide instructions. The NEBB says in their basic instructions it is their responsibility. No balancer I spoke to knew this or did it - 10 points .

3. ASHRAE Thermal Comfort Standard (55-2013) has been modified to include Normative (mandatory) and Informative sections so that it can be referenced directly in codes. ADPI will be included by reference to the ASHRAE Handbooks, which will be updated to show the relationship between air distribution and thermal comfort. Well, this didn’t happen. The ball got dropped somewhere. My bad - 0 points.

4. There will still be no new published, peer reviewed, energy savings data for any of the “energy saving” systems (VRF, displacement, underfloor, or chilled beams), but engineers will continue to claim energy savings compared to overhead systems, to get LEED or Energy Star ratings. Yup. No data - 10 points.

5. The AHRI / ASHRAE study on whole system energy use of fan powered boxes will begin to be integrated into the Energy Plus and possibly Trane Trace and Carrier HAP energy models under an AHRI research program. Underway. An excellent paper will be presented in June - 10 points.

6. The number 1 reason for not renewing the lease in high rise buildings will continue to be “occupant dissatisfaction with the building environment” (ie: comfort). It has been so for the past 20 years and is frankly a ‘gimmee’. One can hope that I miss this one. The BOMA public relations person now refuses to answer this question. I guess they are a bit embarrassed by the data. I’ll give myself 5 points.

7. The market for HVAC components will again be up about 5% with pent-up demand slowly coming back. Slowly but surely it is - 10 points.

8. VAV overhead air distribution will continue to be (by far) the most used system in new buildings. As loads decrease, it will become more apparent that the ventilation load in the interior is the predominant building load. ASHRAE RP 1515 will open a lot of eyes. The report from the ASHRAE MTG on Advanced Air Distribution will be circulated showing paths to optimize system design. The MTG says it has completed its work and has been dissolved. About 20% of the engineers I spoke to have lowered their interior design from 1.0 to 0.65cfm/sf. - 8 points

9. While many VAV box schedules will continue to show design discharge temperatures in excess of 90°F, a number of Engineers will finally get it. (ps: Hot air rises!) I still get push back on this issue, but some are getting it. It’s getting better, but we’re still not there yet - 8 points.

10. Sadly, I predict that the Cowboys will continue to wallow in the mud of disappointment. Ok. I blew this one. Of course, the Cowboys blew the last one! But, I’m still giving myself 0 points.

So I get 71 out 100. That’s just a barely passing grade… but seems familiar some how. I’ll try to do better this year.

Authored by: Dan Int-Hout, Chief Engineer Krueger

Wednesday, January 28, 2015

Top Ten HVAC Predictions for 2015

It’s time for my long awaited top 10 predictions for 2015. I am becoming a bit pessimistic in my predictions. If I get a high score next January, it will mean the industry has failed its customers - building occupants.

1. LEED V4 will get less and less buy-in. Since there is no enforcement or post construction check, the LEED rating has no teeth --- but it gets “feel good” points from the “greens”. None from me though.

2. Installed linear diffusers will still fail to have pattern controllers set prior to balancing. Sadly, this is likely a gimmee. When asked, neither balancers, contractors, or design engineers take any responsibility for assuring this gets done. Building occupants will suffer, but everyone else gets paid.

3. The Variable Volume Series Fan Powered Box will be recognized as a really effective way to design an energy efficient HVAC system.

4. There will still be no new published, peer reviewed, energy savings data for any of the “energy saving” systems (VRF, displacement, underfloor, or chilled beams), but engineers will continue to claim energy savings compared to overhead systems to get LEED or Energy Star ratings. This is likely another gimmee, but I can hope.

5. The AHRI / ASHRAE study on whole system energy use of fan powered boxes will start to be integrated into the Energy Plus and possibly Trane Trace and Carrier HAP energy models under an AHRI research program. This is one I hope I win.

6. The number 1 complaint I hear is that offices get cold in the afternoon. No kidding. Design loads are overestimated by likely a factor of five. I predict this will not change in 2015… Another one I wish to lose.

7. The market for HVAC components will again be up about 5% with pent-up demand slowly coming back.

8. VAV overhead air distribution will continue to be (by far) the most used system in new buildings. As loads decrease, it will become more apparent that the ventilation load in the interior is the predominant building load.

9. While many VAV box schedules will continue to show design discharge temperatures in excess of 90°F, a number of engineers will finally get it.

10. The Cowboys will prove to be unpredictable. After last season, one has hope, but I wouldn’t bet any money. I predict a 9-7 season.

Authored by: Dan Int-Hout, Chief Engineer Krueger