When we were designing the HVAC system for an airport client, we learned a few things that we want to pass on to other engineers. Clients care more about ventilation than ever. Because of COVID-19, they are asking questions about recirculating air between rooms. We agree with them that 100% outside air is a safe bet.

Below is a very abbreviated method that we use for all our DOAS (dedicated outdoor air system) projects:

1. Run the heating/cooling loads as you normally would using TRACE of whatever program you use. Get output that shows envelope loads for each zone. (Ignore the latent load information you get from the program.)

2. Make a spreadsheet showing each zone’s square feet, number of people in the zone, envelope heating load, and envelope cooling load.

3. Calculate ventilation requirements for each zone as you normally would using ASHRAE 62.1 standards. (We use a separate spreadsheet that feeds the ventilation cfm into the spreadsheet from step #2.)

4. In the main spreadsheet, calculate the amount of air you’ll need to cover the latent load. Use the delta h equation from your college days in thermodynamics. (Or look it up online if you were drinking too heavily in college to have accurate recall of those days.) You will need to know the enthalpy (h) of the air leaving your main air handling unit delivering to the zones. This is where you’ll either get the temperature coming from the main unit from the core and shell team, or you’ll decide on it yourself if you are specifying the main unit. If you are specifying the main unit, use a delivery air temperature that is warmer than you’d normally deliver in a standard system - more like 62 F than 55 F.

5. Create a column in your growing spreadsheet to automatically pick the greater of the cfm for each zone - the latent load cfm or the ventilation cfm. Then create another column to add cfm if you want to. That will be key later.

6. Now you have an idea how much air you are delivering to each zone to cover ventilation and latent loads. Create another column to show the sensible cooling load. That sensible load is the sum of lights, equipment, and the occupants’ sensible (not latent) load.

7. Now the fun begins. For areas where you don’t want add radiant systems, pump up the air volume in that column you created in step #5. We do this for very small rooms, places with anti-ligature restrictions, or rooms in which the architect wants to keep the ceiling clear. At this point, you want to pay attention to the size of your main DOAS unit. It only has so much air to deliver, but you can assume that not all areas will be calling for maximum cfm at the same time. Be careful, though, because unlike a standard design that uses lots of cfm for cooling, you don’t have as much diversity to play with. It’s possible that many rooms could be occupied and require their full ventilation requirement.

8. After you are done adding extra cfm to areas, create columns to subtract the cooling that air is doing from the full cooling load you created in #6. (I know. This spreadsheet gets big, but it’s worth it.) The number you get here is the cooling left for the radiant system. You can use it to figure out how many panels or sails you need in each area. Where the area of panels or sails exceeds 80% or so of the ceiling space, you need to go back and add more air to that area.

9. Heating is a little simpler. Use the envelope loads and a reasonable envelope infiltration number to calculate your heating need in each zone. We use terminal units with heating coils for each zone. Interior zones in need of cooling still receive the cool air from the DOAS while the TUs bump up the delivery temperature for perimeter zones in need of heating. Since cooling drives the square feet of your panels and sails, you’ll likely be left with plenty of heating capacity for your perimeter zones. We set up columns in our spreadsheet to check that (Heating provided by TU air +heating provided by sails/panels - heating needed.)

   I know that’s not enough information to execute a full design if you’ve never done it before, but these hints would have helped us on our first 100% OSA design. Checking your latent vs. ventilation cfm and then adding cfm where you want it was key to reducing radiant equipment.

That’s the word we keep hearing about these last six months. COVID-19 has changed the way we live and work. That part truly is unprecedented.

What is too common is the fact that women who are already in crisis and especially women of color are disproportionately affected by the current situation.

Recognizing that we are incredibly lucky to be employed, working from safe homes, and we have never personally had to navigate racial bias, we are making a mid-year donation to Call to Safety. This organization is truly in the trenches helping survivors of abuse. This is not easy work, but they do it with an eye toward racial equity, an understanding of the risks to our LGBTQ brother and sisters, and the recognition that sex workers are real people who deserve to be safe.

These are not easy things to talk about, and especially risky to do so on a company web site. We hope our partners in the industry agree that the time for polite silence about these crucial matters has passed.

We are now certified as a woman-owned business in Washington. We love Washington. One of us was even born there. What’s up, Vancouver? How are you doing, Seattle?

It was an incredible year for us, thanks to the best clients and partners we could ever hope for. As we wrap up deadlines and accounting for 2018, here are a few things that we loved this year, in no sensible order:

We were so excited to receive a DJC Building Diversity award and be the cover shot for the Women of Vision Magazine. If we look a bit flushed in the shot, it’s because it was taken on one of those high-90s afternoons. Still, we were so pleased to represent!

We are fans of the new Appendix N clarifying distinction between Fire Code and what city plans reviewers can enforce. This came out in November 2017, but we got into the details this year and we like the crisp lines created by this appendix. (If you don’t love code as much as we do, we won’t judge you. Just call us if you need help unraveling the details.)

Camo sweaters, tights, and purses. We love them. But we can’t buy any more. We now have so many of each that we must text each other before meetings to make sure we don’t show up in matching camo, like we are on some weird cashmere-clad hunting trip.

Variable refrigerant systems. We’ve been designing and commissioning these for different clients. Moving less air, keeping duct sizes small, and preserving the ceiling space for whatever the architect envisions is pretty darn satisfying.

Wonder Woman stamps. These were first issued in 2016, but they became our official postage in 2018. If you’ve received any checks or love notes from us, you’ll see that they have Wonder Woman stuck to them rocking wrist cuffs. We wear wrist cuffs, too, but ours aren’t bulletproof.

This year, we loved being successful enough to give back to the community. We gave Oregon Tradeswomen a set of welding leathers, hood, and gloves that new welding program graduates can use until they can afford their own. Also, we donated to Call to Safety, a deserving Portland group that helps survivors of trauma and abuse. Our donations are a drop in the bucket compared to the numbers of people each organization serves, but it makes us feel good to be a part of the solution.  

Thank you to our partners and clients for making all of this possible, even the camo sweaters.

What a fast year in Portland construction! There was so much going on and every project was urgent.

Admit it. If you're in construction you like it that way. We LOVE it.

There's almost too much goodness to report in one post, but I'll hit the highlights: 

Jennifer Kaye joined the Bantam Engineering team this year. She is currently commissioning PSU's Stott Center, finishing a plumbing/HVAC design for City of Portland, and diving into a food processing equipment move. For the last six months of design, she took the lead on The Portland Building's 15 floors of HVAC TI design which was just completed. 

Thank goodness Jennifer also grew up in Alaska. We have the same grit that you only get from below zero temperatures and a lack of fresh fruit. (Alaska humor.) 

We're feeling pretty damn proud of the work we did for our high tech, education, medical, industrial, and municipal clients. We have made some awesome new architect friends and we're looking forward to some exciting work in 2018!

Do other engineers get a little sentimental when they stamp a design?

I got my Oregon professional engineering license in 2003, but didn't stamp drawings for years. I was doing a lot of design and construction management and commissioning, so I didn't need to bust out my stamp and sign any drawings. Now that I'm designing HVAC systems, process piping, and plumbing, I stamp and sign drawings. Whenever I do, I think of how much I learned in school, on the job, and from other engineers to get here. I'm also aware of how much the rest of the world trusts engineers to get it right. Every time I put a stamp on a drawing, it feels like a little ceremony of gratitude and responsibility.

Last week I had the great pleasure of writing a code assessment to accompany a design for a high-tech client. That may sound like I'm being sarcastic, but I'm not. I honestly love analyzing building, fire, mechanical, and energy code to find the right solution for my client and make the most succinct presentation to the Authority Having Jurisdiction. Yes, the codes make crazy circular references to one another and the language is awkward and full of double negatives, but that's part of the fun. Understanding code and applying it in a way that works for my clients - and then making the case to the AHJ is truly a good time for me.

This week I dove into a bit of work that allowed me to flip through my 1969 hardback copy of Keenan and Keyes Steam Tables. I love this book. It smells like an old library and has a poster-sized pullout Mollier diagram.

It's okay if you don't get as geeked up about enthalpy and specific volume as we do. That's why we are engineers. We love boilers, chillers, and heat exchangers enough for all of us.

Could your organization use template specifications for commissioning, training, and closeout? They are a great way to make sure projects are delivered in the same way every time - complete and ready for occupancy.

We love to write smart specifications. Let us help!

Getting a project's building permit quickly and painlessly involves more than just knowing code and design package contents. It involves a bit of negotiation and personal touch. We have that. We can be your permit people.

If you like the freedom of choosing different design teams for multiple projects, you'll still have the same contact with your jurisdiction for all of those projects. That can make life so much easier. And that's what we want.