Every house gets a Manual J, and you get the report

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.

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.