Pool Houses & Detached Structures | HVAC Options in Texas

Sizing notes: Add 50% capacity for garage door heat gain. A 500 sq ft garage may need 18,000-24,000 BTU.

Sizing notes: Account for humidity load—may need larger unit or dedicated dehumidifier.

Sizing notes: Size like any living space—manual J calculation recommended. Typically 400-800 sq ft range.

Sizing notes: Add 400 BTU per computer/equipment. West-facing windows add significant load afternoon.

Sizing notes: Depends entirely on what's stored. Most storage doesn't need AC.

Sizing notes: Size for peak occupancy—add 600 BTU per person expected during gatherings.

For Texas heat, a ductless mini-split is the most effective solution for a detached garage you use regularly. It handles 100°F+ days efficiently and provides heating in winter. For occasional use, a garage-specific wall unit ($1,500-3,000) or large window unit ($300-500) can work, though they'll struggle on the hottest days. Critical: insulate the ceiling and garage door first—an uninsulated garage will overwhelm any AC unit in Texas summer. Budget $1,000-3,000 for insulation before investing in cooling equipment.

It's technically possible but rarely advisable. Problems include: long duct runs lose efficiency (2-3% per 10 feet), your home system may not have spare capacity, underground or overhead ductwork is expensive ($3,000-8,000+), and you lose independent zone control. A mini-split ($3,500-6,500) almost always costs less, works better, and doesn't affect your home's comfort. The only scenario where extension makes sense is if structures are within 15-20 feet and your current system is significantly oversized.

Standard calculations don't work well for garages due to poor insulation and frequent door opening. Rough guidelines for insulated Texas garages: 1-car garage (250 sq ft): 12,000-15,000 BTU, 2-car garage (500 sq ft): 18,000-24,000 BTU, 3-car garage (750 sq ft): 24,000-30,000 BTU. Add 50% if uninsulated, 25% if garage door opens frequently, and 20% for workshops with heat-generating equipment. For living spaces like ADUs, use standard 20-25 BTU per square foot plus Manual J factors.

For Texas workshops, portable AC is generally not recommended. Single-hose portable units are extremely inefficient—they exhaust hot air outside but create negative pressure that pulls hot outside air in through cracks. Dual-hose models are better but still less efficient than window units. A 12,000 BTU portable might provide effective cooling equivalent to an 8,000 BTU window unit. Portable AC makes sense only if: you rent and can't modify the structure, you need to move the unit between locations frequently, or you have no windows and can't install other options.

A window unit can provide some relief but will struggle in extreme Texas heat (100°F+), especially in uninsulated garages. Realistic expectations: it may lower temperature 10-15°F below outdoor temp—so 85-90°F when it's 105°F outside. For a 500 sq ft garage, you'd need at least 14,000-18,000 BTU. Window units also can't overcome the heat surge when you open the garage door—it may take 30-60 minutes to recover. For comfortable working conditions in summer, a mini-split is a much better investment.

Total installed cost for a mini-split in a detached structure typically runs $3,500-6,500 in North Texas. This includes: equipment ($1,500-3,000 depending on size and brand), installation labor ($1,000-2,000), electrical work ($300-800 for dedicated circuit), line set and mounting ($200-500), and permits if required ($100-200). Multi-zone systems or longer line runs add cost. Some contractors offer package pricing. Get 2-3 quotes and verify the price includes all electrical work—some quote HVAC only and electrical separately.

Absolutely yes. Insulation before AC is almost always the better investment for Texas detached structures. An uninsulated garage in summer can reach 120-140°F, overwhelming any reasonable AC system. Key insulation priorities: ceiling/attic insulation (most important—heat enters through roof), garage door insulation kit ($200-500), and radiant barrier ($0.50-1.50/sq ft). A well-insulated garage might only reach 90-95°F without AC, making any cooling system work effectively. Budget $1,500-3,500 for comprehensive garage insulation—it pays back in equipment sizing and operating costs.

Pool houses need equipment that handles high humidity from the pool and frequent door opening. A ductless mini-split with dehumidification mode is ideal—look for units with 'dry' mode that removes moisture without overcooling. Consider: corrosion-resistant equipment (chlorine exposure damages standard units), slightly oversized unit to handle humidity load, and a model rated for high-humidity environments. For pool houses over 600 sq ft, consider a dedicated dehumidifier in addition to AC. Budget $4,000-7,000 for a properly specified pool house system.

Permit requirements vary by municipality in Texas. Generally: ADUs and guest houses almost always require permits for HVAC, pool houses may require permits if adding electrical or if structure isn't already permitted, garages and workshops typically don't need permits for window units but may for permanent installations, and new electrical circuits usually require electrical permits. Check with your local building department. Even if not required, permitted work provides documentation for insurance and resale. Permit costs typically run $100-300.

A home office in a detached building needs reliable, quiet cooling since you're there all day. Best option is a ductless mini-split—it's efficient, quiet (indoor units around 25-30 dB), and maintains consistent temperature. Size for: base square footage (20-25 BTU/sq ft), add 400 BTU per computer, add 20-30% for west-facing windows, and consider humidity control for electronics protection. A 12,000-15,000 BTU mini-split handles most detached offices well. Operating cost is typically $25-40/month with daily use, much less than the productivity cost of being uncomfortable.

Only in West Texas where humidity stays low (below 30-40%). In North Texas and most of the state, summer humidity of 50-70% makes evaporative coolers (swamp coolers) nearly useless. They work by evaporating water, which doesn't happen when air is already humid. Even in dry climates, they add moisture to the air—problematic for workshops with tools that rust or spaces where humidity control matters. If you're in a dry area, evaporative coolers can be very economical (pennies per hour to operate), but they're not true air conditioning and won't achieve the same comfort level.

The cheapest approach depends on your usage pattern. For occasional use: fans and ventilation ($50-200)—don't expect cool, just air movement. For moderate use: window unit ($150-400) if you have a suitable window, or portable AC ($300-600) if not. For frequent use: the cheapest effective option is actually to insulate first ($500-1,500 DIY), then add a window unit. A well-insulated space with a $300 window unit will be cooler than an uninsulated space with a $3,000 system. For daily all-day use, a mini-split has the lowest operating cost over time despite higher upfront investment.