HVAC, Air Quality, and Building Performance

MECHANICAL SYSTEMS

HVAC, Air Quality, and Building Performance

TYPICAL ALLOWANCE: $120,000 - $350,000 MECHANICAL AND ENVELOPE

Homeowners rarely tour a mechanical room, but the mechanical and envelope package determines whether a house feels like the photographs suggest it should. A beautifully finished residence that runs humid in July, is loud when the system cycles, or has a primary suite three degrees warmer than the great room has failed at something more fundamental than finish selection.

In Charlotte, the governing variable is latent load. Our summers deliver long stretches of high dew point, and a system sized only for temperature will satisfy the thermostat while leaving indoor humidity well above comfortable.

Zoning and equipment selection

We design for multiple independent zones rather than a single system per floor: primary suite, secondary bedrooms, main living, and any space with a distinct load such as a gym, wine room, or west-facing sunroom. Each zone has its own thermostat and its own sensible and latent calculation.

Variable-capacity equipment is the standard specification. A modulating system running at 40 percent capacity for long periods removes far more moisture and produces far less noise and temperature swing than a single-stage unit cycling on and off. The comfort difference is immediate and permanent.

Load calculations are performed room by room per Manual J with actual glazing areas and orientations, and duct systems are designed per Manual D. Rule-of-thumb sizing — still common even in expensive homes — produces oversized equipment that short-cycles and never dehumidifies properly.

Humidity and ventilation

Whole-house dehumidification is standard in our residences, ducted so it can operate independently of cooling. This is what holds a house at 45 to 50 percent relative humidity in shoulder seasons when the cooling load is too small for the air conditioning to run.

Because a well-built house is tight, mechanical fresh air is required. We specify an energy recovery ventilator that brings in filtered outdoor air while transferring heat and moisture to the exhaust stream, controlled to deliver a measured rate rather than relying on infiltration.

Filtration is specified at MERV 13 minimum on a deep-pleat media cabinet sized so that the higher filtration does not restrict airflow. Where allergy concerns are present, we add HEPA bypass or bipolar ionization at the air handler.

Insulation and air sealing

Mechanical performance depends on the envelope. Our standard approach uses closed-cell spray foam at the roof deck to bring attics and their ductwork inside the conditioned envelope, with dense-pack or open-cell in walls and rigid continuous exterior insulation where the assembly allows.

Air sealing is verified rather than assumed. We blower-door test before drywall, when leaks are still accessible and inexpensive to correct, and again at completion for documentation. Rim joists, top plates, chases, and can penetrations are the recurring culprits.

Duct systems are sealed with mastic and pressure-tested. Leaky ducts in an unconditioned attic are among the most expensive defects a home can carry, and they are invisible to a homeowner for the life of the house.

Budget and long-term operating cost

A complete mechanical and envelope package for a 6,000 to 9,000 square foot residence typically runs $120,000 to $350,000, covering multi-zone variable-capacity equipment, dehumidification, energy recovery ventilation, filtration, spray foam, and testing.

The operating case is straightforward. Right-sized modulating equipment inside a tight, well-insulated envelope with sealed ducts consistently uses substantially less energy than oversized single-stage equipment in a leaky one — and it is quieter, more even, and drier every day of its service life.

Charlotte comfort is a humidity problem. A system that satisfies the thermostat and leaves the house at 60 percent has not done its job.

PETERS CUSTOM HOMES

AT A GLANCE

Specification Summary

FREQUENTLY ASKED

Climate & Air Questions

Why is my new luxury home humid even when the air conditioning runs?

Usually oversized single-stage equipment. It satisfies the thermostat quickly and shuts off before removing meaningful moisture. Variable-capacity equipment sized by a room-by-room Manual J calculation, paired with whole-house dehumidification, resolves it.

How many HVAC zones does a large custom home need?

We zone by load rather than by floor. A 7,000 square foot residence commonly has four to six zones: primary suite, secondary bedrooms, main living, and any space with a distinct load such as a gym, wine room, or heavily glazed sunroom.

Is spray foam insulation necessary?

It is our standard at the roof deck because it brings the attic and its ductwork inside the conditioned envelope, which eliminates the largest efficiency loss in a typical Carolina home. Wall assemblies can be dense-pack or open-cell with continuous exterior insulation depending on the design.

What is a blower door test and when should it happen?

It measures whole-house air leakage. We test before drywall, when leaks are still accessible and cheap to seal, and again at completion for documentation. Testing only at the end tells you the number without giving you a practical way to improve it.

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Discuss Your Specifications With the Founder

Nicholas Peters personally reviews every specification decision on the eight to ten residences the firm builds each year.

LIMITED TO 8–10 PRIVATE RESIDENCES PER YEAR