The questions we are asked most often

Air at 5,280 ft is about 17 percent less dense than air at sea level. Everything that moves air or burns gas notices.

The sensible heat equation is the clearest example. At sea level it is Q = 1.08 x cfm x delta T. In Denver the constant drops to roughly 0.90, so the same air handler moving the same cfm removes about 17 percent less sensible heat. Fans also generate less static pressure at reduced density, and gas equipment above 2,000 ft needs a high-altitude orifice kit and a derated input.

A catalogue selection made on sea level data is therefore optimistic on capacity and wrong on airflow. Every selection we make is corrected for site elevation, and the correction is shown on the selection sheet.

Every house, and you get the report. It lists the inputs we used: orientation, glazing area and U-value, infiltration assumption, insulation levels, and the design conditions.

The reason is not paperwork for its own sake. Oversized equipment short cycles, never reaches steady state, dehumidifies badly and wears its compressor out early. In a Denver retrofit the honest load is very often 20 to 35 percent below the equipment that is currently sitting there.

If you disagree with an assumption in the report, that is a useful conversation to have before the equipment is ordered rather than after.

A properly selected cold-climate heat pump will, and we will show you the number rather than assert it.

The Denver 99.6 percent heating design condition is about 1 F. A modern variable-capacity cold-climate heat pump typically holds 70 to 80 percent of its nominal heating capacity at that temperature. We select on capacity at the design temperature, not at the 47 F rating point, and we calculate the balance point where the heat pump output crosses the building load.

For most well-insulated Denver homes that balance point lands between 5 F and 20 F. Below it you need supplemental heat, and how much depends on your house. We size the supplement to the gap, which is usually far less than a full backup furnace.

R-454B has a global warming potential of about 466, against roughly 2,088 for R-410A, which is why the AIM Act phase-down moved new equipment manufacture onto it.

R-454B is an A2L, which means mildly flammable. Practically that changes charge limits per occupied space, requires refrigerant detection and mitigation on some indoor equipment under UL 60335-2-40, and changes some service procedures. It does not make the equipment exotic or hard to maintain.

Existing R-410A systems are not illegal and do not need replacing. Reclaimed and stockpiled R-410A remains available for service. We will tell you plainly whether a repair or a replacement is the better spend on your specific unit.

Usually, yes. Roughly speaking, if the equipment is right and the comfort is wrong, the distribution is the suspect.

The first measurement we take is total external static pressure. Most residential air handlers are rated at 0.5 in. w.c. We routinely measure 0.9 to 1.2 in. w.c. on systems that were installed last year. That means the blower is not delivering rated airflow, which shows up as one room that never gets there.

The fix is usually a return path, a filter rack, or two or three fittings with a bad equivalent length, not a bigger blower. We measure, we show you the readings, and then we design the correction to a friction rate.

Almost certainly not directly in the duct. A true HEPA filter removes 99.97 percent of 0.3 micron particles, and it does that by presenting a pressure drop that a normal residential or commercial air handler cannot overcome.

For nearly all buildings the right answer is MERV 13 in a properly sized filter rack with enough media area to keep the pressure drop low, which is what ASHRAE recommends for general indoor air quality. A four-inch MERV 13 in a deep rack usually has a lower pressure drop than the one-inch MERV 8 it replaces.

If you genuinely need HEPA, for a clean space or a specific process, it goes in a dedicated recirculating unit designed around it, with its own fan.

ASHRAE 62.1, ventilation rate procedure. The breathing zone outdoor airflow is Vbz = Rp x Pz + Ra x Az, where Rp is the rate per person, Pz is the zone population, Ra is the rate per unit area and Az is the floor area.

For an office that is 5 cfm per person plus 0.06 cfm per square foot. The number that comes out of that is frequently different from the number the existing system delivers, particularly after a tenant changes the use of a space.

We calculate it, we set the outdoor air damper to deliver it, and we trend the result so it can be shown to have been delivered rather than assumed.

TAB is testing, adjusting and balancing. Airflows and water flows are measured against the design, dampers and valves are adjusted until they match, and the results are recorded.

It is a separate line because it is separate work, and because listing it separately makes it harder to quietly delete. A system that was designed correctly and installed correctly still does not perform correctly until it has been balanced.

You get a TAB report with the design value and the measured value side by side for every terminal. Where a terminal is out of tolerance, the report says so and says what was done about it.

Yes, for service, maintenance agreements and repairs. That is most of what a mechanical contractor does.

For a replacement we will always re-run the load and measure the existing distribution before quoting, even if the equipment is a straight swap on paper. It is the only way to avoid inheriting somebody else’s sizing error at a higher price.

If the honest answer is that your existing system has years left and needs a repair rather than a replacement, that is the answer you will get.

Maintenance agreement holders get a four hour response target during business hours and 24 hour coverage, including weekends and holidays, with a named account engineer who already knows the building.

Without an agreement we schedule against available capacity, which in a July heat event or a January cold snap can mean a wait. That is not a sales tactic, it is arithmetic about how many trucks exist.

Every visit, agreement or not, ends with recorded readings in your log rather than a verbal summary.