TUCSON, AZ — Installing the hvac system for a multi-million dollar custom home here was a real challenge for Marshall Dennington, owner of Temco Air Environmental.

In this project, the homeowners specified that their winter home look just like a 200-year-old Spanish monastery, complete with high ceilings and double-thick “Rastra”-block walls. However, the owners didn’t want to see, hear, or feel the hvac system when it turned on and off.

Since Spanish monasteries didn’t have heating and cooling systems, let alone soffits to run any ductwork, Dennington specified a high-velocity air conditioning system, as it only requires a 3 1/2-in. space to run the supply duct. The flex tubing could be run under the floor, terminating at 2-in. round outlets rather than standard registers.

But then there’s that quote about the best laid plans.

In this case, after the foundation was poured and Dennington started the installation, the owners decided to enlarge the planned 6,000-sq-ft home by 2,000 sq ft. Then it was decided that the mechanical room off the master suite would have its height cut in half. So it was back to the drawing board.

Equipment changes

Dennington now says the changes he had to make weren’t really too bad.

“We had to re-engineer the sizing on the equipment and obviously recalculate everything to make sure we were supplying adequately sized equipment to maintain comfort levels,” he says.

“We basically upsized our boiler and some of our air-handling equipment and air conditioning tonnages to accommodate the changes.”

The house’s hvac system now consists of five Unico high-velocity systems (three 5-ton systems, one 2-ton system, and one 3-ton system), each of which uses a direct-expansion, high-efficiency Carrier air conditioner and a hydronic heating coil. Each system also has high-efficiency Honeywell filters and humidifiers.

The bathrooms and shower areas make use of in-floor radiant heat. A Trianco “Heatmaker” 270,000-Btu boiler picks up the in-floor radiant heat, as well as the hydronic heat for the forced air. The boiler is also connected to two 60-gal Phase III indirect-fired water heaters and is capable of making up 300 gal of 180°F water an hour.

Since Spanish monasteries didn't have heating and cooling systems, let alone soffits to run any ductwork, Marshall Dennington, owner of Temco Air Environmental, specified a high-velocity air conditioning system.

Control from behind the scenes

The house has five zones controlled by two panels with microprocessor controls and zone valves. One control panel is in the main mechanical room and the other is in the master suite mechanical room.

The owners said they wanted easy-to-use controls, so Dennington used very simple thermostats that were run back through the microprocessors.

All the thermostat functions, such as timing and programmability, are behind the scenes.

“We wanted the ability to provide setback and energy savings, but the owners did not want a modern-looking programmable thermostat. We used electronic time clocks to accommodate that, much as though you’d have on a lighting circuit. That gives us the programmability,” says Dennington.

More changes, greater difficulty

A bigger challenge for Dennington was trying to figure out how to put all the equipment in the now-halved mechanical room off the master suite. The owners decided midway that they wanted to install a poured-in-place concrete bathtub where the mechanical room was going to be located.

Dennington compensated for that by jackhammering out the existing slab and sinking the mechanical room 2 ft.

Then he had a brainstorm. As long as the new tub was sitting on top of the mechanical room, why not wrap it with in-floor radiant heat? Dennington says this solves the problem of bath water becoming too cold too quickly.

“When you fill this thing up with hot water, the radiant heat keeps you nice and toasty for a long time,” he says.

The biggest problem Dennington had with the now-smaller mechanical room (30 in. deep by 60 in. wide by 60 in. high), was how to arrange the equipment for serviceability.

“In that very small mechanical room we’ve got a 2- by 3-foot control board, a 60-gallon hot water heater, an air handler, an air conditioning coil, a hydronic heating coil, a high-efficiency filter, a humidifier, and circulation pumps,” says Dennington.

“But we were able to make it so every valve, every control, and anything that needs to be serviced is very accessible.”

That will ultimately make it easier for Dennington, who has a service agreement with the new owners to keep the system running in tip-top shape.

Must fit in with monastery design

In addition to providing the comprehensive hvac system (priced around $140,000), Dennington had to go one step further. He had to make it look like it belonged in a 200-year-old Spanish monastery.

For example, the house needed over 100 outlets to provide the occupants with complete comfort.

“Hiding 124 outlets was quite a challenge at times,” says the contractor. “And we custom made the outlet covers so they would be of the same wood as the ceiling, which was made from wooden slats taken out of a barn in Pennsylvania.”

Even the return air grilles were custom made. Dennington manufactured them in his shop out of old steel that was then sprayed with a solution to make them rust, creating the old look the owners required. But he main goal was to keep everything as hidden as possible, says Dennington.

That went for the thermostats as well, which were painted to match and blend in with everything, because obviously a 200-year-old building wouldn’t have electronic devices on the wall.

The result is truly spectacular, and the owners are thrilled, says Dennington, who is also pleased with the way the project turned out.

“I’m proud of the way it looks and how it’s hidden. I’m also proud of the mechanical rooms — the neatness, the ease of monitoring everything, and the ease of servicing it. The overall aesthetics and comfort level worked out very well.”

Sidebar: No cold showers here

As you might imagine, the bathroom in the master suite is no ordinary bathroom. This one contains an immense shower, measuring 7 by 8 ft with a 22-ft-high ceiling. At the top of the shower are huge cathedral windows.

Dennington had to put in a 600-cfm exhaust fan to eliminate condensation on the ceiling and windows.

“The fan duct is pitched back to the shower and sealed, much as though you’d do in a dishwasher, so that the water that does condense runs back into the shower,” says Dennington.

His main concern was keeping the condensate off the windows so they wouldn’t drip and scale.

Completing the luxurious bathroom is in-floor radiant heating, which keeps the stone floors of the shower and bathroom comfortably warm.

Sidebar: Fireplace solution

Another interesting problem emerged during the construction of this home. It turned out that the fireplace in the great room was so large, there was no room for the ductwork to pass through.

The beams were originally designed to rest on the fireplace, but since that blocked the ductwork, Dennington had to come up with a solution.

“We fabricated a steel duct and laid the beams on top of that,” he says, “so we have a structural piece of duct in there. It’s just a large steel tube beam that the rest of the beams sit on.”

The beams came from the same barn in Pennsylvania that supplied the slats for the ceilings.