Selection of HVAC System for Habitat for Humanity
This project involved performing a full HVAC load calculation and system selection for a residential construction located at 555 Garden Street, Hartford, CT. The analysis included winter heat‑loss calculations, summer cooling‑load modeling, envelope U‑value determination, ventilation requirements, and garage thermal behavior.
The goal was to determine accurate heating and cooling loads to size equipment appropriately and ensure year‑round comfort, energy efficiency, and compliance with industry standards. Using the following design conditions.
Winter: 7.52°F dry‑bulb, 30% RH
Summer: 88.34°F dry‑bulb, 74.48°F wet‑bulb, 50% RH
Indoor Setpoints: 75°F heating, 75°F cooling
Air Changes per Hour (ACH): 0.3
Location Reference: Hartford, CT climate data
Heat Loss
Winter heat‑loss calculations were performed using U‑values derived from wall, roof, floor, and slab assemblies. Each building surface was evaluated using:
U‑value × Area × ΔT
Ventilation losses based on ACH and air density
Envelope components including windows, doors, and basement walls
Cooling Load
Cooling loads were calculated using CLTD (Cooling Load Temperature Difference) tables for July and August. The model incorporated:
Solar heat gain through glass (orientation‑dependent)
Internal loads from occupants, lighting, and equipment
Ventilation and infiltration loads
Roof and wall solar absorption
Final HVAC Selection
The prescribed HVAC solution is a Carrier 25HCD Comfort 13 heat pump using Puron refrigerant, providing both heating and cooling through a reversible vapor‑compression cycle. The selected 25HCD348 outdoor unit paired with the FB4CNF048 indoor section meets the 60,000 BTU/hr heating load while delivering efficient airflow and balanced performance. Though slightly undersized, the system operates more efficiently over longer cycles and reduces long‑term operating costs..
Uses Puron (R‑410A) refrigerant with SEER 13, EER 10.5–12.5, and HSPF 7.7–8.2.
Equipped with a scroll compressor, internal pressure relief, and thermal overload protection.
Includes high‑pressure and loss‑of‑charge safety switches for system protection.
Provides up to 1800 CFM and operates between 3.5–6 kW under design conditions.
Cooling capacity reaches 58.09 MBtuh total and 30.71 MBtuh sensible.
Procedure and findings were summarized and presented as follows: