In my previous feature, I mentioned a large in-floor heating job I did for a municipal garage back in 2003. At the time this municipal garage was being planned, I was still an independent contractor employing four to six plumbers, depending on the workload. I was signatory to the local union and would use guys off the bench as needed. In this feature, I’ll expand on the details of this fun project. 

During the late fourth quarter of the construction year, I would go to the local plan room in search of projects for bid the following summer. Back in 2002, the plan room had a website, which listed upcoming projects, rather than having a file of complete plans available to download. I would scan the list for interesting projects and then go to the plan room to look at the print.

If I found a project I wanted to bid, I could have the pages printed and take them back to my office.

I’m probably showing my age, but I still think there is nothing better than unrolling a big print on a table to work up the quote! I can write notes, highlight walls and details, and read comments written by the engineer. It’s so easy to scan the lower righthand corner on each page to quickly find the exact page I need. For me, I find looking at prints on a computer screen very cumbersome. Don’t get me wrong, I am all for using less paper, but if there is a rolled-up print, I’ll use it.

In 2002, I saw the 33,000-sq.-ft. municipal garage project scheduled for the spring of 2003 in a town 30 miles away from my shop. I really couldn’t believe my eyes at first; they wanted in-floor heat! It was going out for public bid and as “design-build.” Normally I am not an advocate for a municipal public bid to be design-build. In my experience, these designs have gone more to “who can do it the cheapest” rather than getting a good quality install in the end for the taxpayer.

But in this case, it noted, “all bids would be reviewed and chosen by the city council for approval.” To me, this meant it wasn’t all about price, and they wanted to get the best bang for their buck.

An advantage

I felt I had an advantage on this job. Where I live there aren’t many contractors capable of doing an in-floor system of this scale. I had been studying and learning about radiant heat for eight years at that time. Granted, I hadn’t done a project of this scale before, but I knew how to do it.

I could also design it in a way most others would not. I used the brand, HeatLink from Calgary, Alberta. HeatLink had developed a very easy-to use Excel-based spreadsheet to calculate heat loss along with their design program. I used their heat loss calculator and design program for every house and small commercial project and it never failed me. Using this program, I had all the loops, manifolds, flow rates, zones and pipe sizes figured out. It would give me a material list as well. HeatLink had a very nice modular manifold called TwistSeal with a 1 ½” sup/ret that could handle up to 22 gpm.  

As a contractor I was not set up for the “VAC” part of HVAC. This project required VAC in the design and bid. To help bid the VAC part of the design, I went to the contractor who I worked for during my plumber’s apprenticeship because his business focused mainly on forced air projects rather than plumbing and heating. I incorporated their design and quote with my final municipal garage design and bid.  

After submitting my design and bid, I was a bit surprised to learn that only five in-floor bids were submitted. The city council met with each bidder to explain the designs. After the council met with all contractors, it was revealed that the other four contractors used the same design supplied to them by a local wholesaler. The fifth design was mine.

This confirmed my prediction that no other contractors in our area had the knowledge and experience to design an in-floor radiant heating system as I could.

Something different

Imagine the city council, after having sat through four identical proposals, finally receiving a proposal unlike the others. They were intrigued to see something different. They had plenty of questions for me to answer. Because I created the design, I had all the answers.  By the end of my presentation, I felt very good about getting the job.  

However, I still had to deal with the local general contractor. The general contractor was surprised to see that the cost of my proposal compared to the other proposals was so close. My bid was the highest, but when I combined my plumbing bid together with a small discount, I was awarded the job! 

The four other bidders, who used the local wholesaler design, were using cast-iron boilers and a staging controller with a primary/secondary runaround loop and injection mixing. They also listed the use of many zone pumps. To me, this was a very “old school” and inefficient design for the city to operate.

During my meeting with the council, l was asked why the other contractor designs listed 15 pumps on their quotes while I only had five.

I said, “I can sell you 10 more pumps, but why buy what you don’t need?”

My mechanical room design was simpler and would be much more efficient. At the time there weren’t many commercial condensing boiler options on the market. I chose to use just one 1,000 MBH modulating condensing boiler for the in-floor load. This boiler was a high-mass fire tube and was great for a variable/primary design. 

Some might ask, “Only one boiler?” The city council certainly did ask.

I explained that one needs to keep in mind the ventilation requirements for make-up air. This was done using a rooftop direct-fired makeup air unit. If, for some reason, the only boiler went down, then they would have backup heat.

The city had one requirement on the plan calling for 100,000 BTU, gas-fired, unit heaters at each of the four overhead doors. This insured more backup heat. In the office area, we used a furnace for the AC and ventilation, so the offices had backup heat, too.

The other bids had a total of 1,500 MBH using three cast-iron boilers. These cast-iron boilers needed return water protection at 140 degrees. As a result, they were incorporating a large runaround loop with closely spaced tees where the boilers and takeoffs were tied in for the variable injection mixing pumps.

They also had many zone pumps for each of the manifold locations. I just remember the total of 15 pumps, and that was not counting the three, one on each boiler. Really then, it was 13 more circulators than my design. Just think of the electrical savings overtime! I had just five different zones using a small Taco circulator. The largest zone was a 0011. There were four smaller zones required in the office area, and I used zone actuators on that manifold. 

Tubing

For tubing, I used 5/8-inch PEX; mostly 500-foot loops in the main garage area. I switched to ½-inch in the small, zoned offices. For the remote office manifold, I ran underground insulated 1-inch PEX sup/ret lines. I also needed one other remoted manifold for the large wash bay zone. Again, I ran underground insulated 1-inch PEX sup/ret lines.

Other manifolds worked out well to be in the mechanical room which was centrally located. The TwistSeal manifolds allowed for many loops because of the modular design, and they all required less than 22 gpm. In the mechanical room, on the dividing wall of the building, I had four different manifolds. The largest of the four had 14 loops, then 12, 11, and 10. The one 12-loop manifold was combined with the remote 10-loop manifold for the large wash bay area. The result was a very nice, easy and clean installation.

Some might argue about the use of 500-foot loops of 5/8-inch PEX. One of the main arguments against 500 feet is the total amount of head loss, correct? In a commercial space, the goal is to heat the building. In a residential space, the goal is comfort. In a large and open garage, where plow and gravel trucks park, no one is walking around barefoot feeling the floor temperature difference like they might on a tiled kitchen floor.

Keeping this in mind, the design delta T could be up to twice that of a residential floor. Also, the tube spacing can be up to twice as well. Increasing the delta T decreases the required flow rate in each loop. This keeps the friction loss within acceptable limits, no glycol in the system in 2003, just water. Using the HeatLink heat loss program, I can change the supply temp, delta T, and tube spacings to make sure the space is still heated properly with no BTU shortages. I designed the tubes to be laid with two loops close to the outside walls at 6-inch centers. Then a couple at 9-inch, then 12-inch, and as much as 18-inch in the center for this job.

Remember, the plan included gas-fired unit heaters by the overhead doors. They won’t be needed if the floor is tubed the way I design it. I loop parallel to the entire width of the door opening using 6-inch centers back into the building the same distance as the height of the door. In this case the doors were 16-feet tall x 14-feet wide. The 6 inches of concrete in that door area can store a lot of extra BTUs, so when that door opens you can just see the explosion of heatwaves being expelled to make up for the heat loss.

When I went back during the winter, they told me that the unit heaters never came on. During the preliminary city council meeting, I failed to convince the committee that these gas-fired unit heaters were not needed, but after they saw my system in operation, they had to agree with me. 

Energy savings

Several years later I wanted to see how well the building was saving energy. So, I compared it to their old garage that was only 25,000 sq/ft. It wasn’t a perfect comparison, but it would have to do. We looked at the budget for the cost of natural gas during the last year in that old building. I was told it had a budget of 20K that year, and the new building only cost them 9K.

Another comparison I used was the Pepsi warehouse in the same industrial park which was very similar in size with newer construction. I obtained permission to see the gas records for the Pepsi warehouse. This warehouse used all air handlers with direct fired-makeup units, and the inside temperature was set lower than that of the city garage. So, the savings would have been even greater than indicated if the inside temperatures were the same. With that said, the Pepsi warehouse was at 12K that year while the city garage was only 9K!

Can you think of one more heating load need of the city garage system, over the warehouse? Just imagine a very cold northern Wisconsin winter night where all 10 plow trucks comeback to park inside the building. What kind of load does that add? People who use that building told me how pleased they were to see how fast the snow and ice melts off the trucks and how quickly everything dries.

For me, this project was great fun overall. I wished I could do many more that size. It was so special to go back and talk to a very satisfied city administrator. He was the guy who really wanted the in-floor heating system. It was he who talked the old guys, on the city council, into spending a little extra money for a more efficient and economical system over the long run.

After I was awarded to job, he came up to me and said, “This better work, or I’m out of a job.”

 I smiled and said, “You’ll be employed for a long time.” 

After running his own business for many years, Ted Schmelling made the switch to becoming a manufacturers rep. He’s currently territory sales specialist at Hot Water Products Inc., Milwaukee, Wis.