🛠 Garage Winter Heating Plan — Temporary Setup with VEVOR Diesel Heaters
Project context: Two VEVOR Diesel Air Heater All-in-One (8 kW / 27,296 BTU) units will serve as the primary heat source during the 2025-26 winter while the garage interior (electrical, insulation, drywall) is completed. Once finished, these units will become backup/auxiliary heaters for the garage and house.
Mounting decision: Both heaters will stay inside the garage on fire-safe pads to keep electronics and fuel warm. Combustion intake and exhaust will route through an insulated window insert built from fiber-cement board + 316 SS thru-hull fittings, keeping fumes outside while recirculating indoor air through the heat exchangers for maximum efficiency.
Strategic Note: The permanent radiant floor heating system (boiler + PEX) is planned as a supplement to VEVOR heaters. However, radiant heat installation depends on electrical service and gas service availability (Stage 6, projected late December/early January at earliest). See Winter Construction Strategy for a detailed analysis of winter construction approaches and boiler installation timeline.
🔢 Heat Load Overview
Garage dimensions: 24 ft × 40 ft × 10 ft = 9,600 cu ft (≈ 960 sq ft) Location: Michigan (Climate Zone 6, 45th parallel)
| Condition | Estimate | Notes |
|---|---|---|
| Poor insulation | 60–80 BTU/ft² | Uninsulated walls & doors |
| Moderate insulation | 35–45 BTU/ft² | Planned final condition |
| Current (uninsulated) need | ≈ 44,000–59,000 BTU/hr | To maintain 40–50 °F inside at 0 °F outside |
| Two × VEVOR 8 kW | ≈ 54,600 BTU/hr (rated) / 38–46 k BTU (realistic) | Covers lower end of requirement |
Result: → Adequate for above-freezing and workable conditions, marginal for “shirt-sleeve” comfort in sub-zero weather.
🌡 Expected Performance
| Outside Temp | Approx. Indoor Temp | Comfort Level |
|---|---|---|
| 20–30 °F | 50–55 °F | Comfortable with light jacket |
| 0–10 °F | 40–50 °F | Chilly but workable |
| Below 0 °F | 35–45 °F | Above freezing; add spot heat for comfort |
🧱 How to Improve Winter Comfort
1. Seal Air Leaks
- Weather-strip overhead and entry doors.
- Foam around windows, conduits, and sill plates.
- Close off any ridge vents or open soffits temporarily.
2. Temporary Insulation
- Staple 4–6 mil plastic sheeting over open stud bays or door backs.
- Use 1–2″ foam board or moving blankets behind work areas.
- Keep materials clear of heater intakes and exhaust.
3. Zone the Space
- Place one heater aimed across the main bay, one near the plumbing/work zone.
- Add a small oscillating fan to destratify warm air.
4. Pre-Heat Routine
- Run both heaters on high 30–60 min before working.
- Drop to mid-power to maintain target temps.
5. Supplemental Spot Heat
- A 120 V or 240 V electric radiant or fan heater at the workbench makes a big difference on very cold days.
6. Limit Door Openings
- Opening the main door dumps stored heat—plan material moves, then re-heat with both units at high output.
⚙️ Setup & Safety
| Item | Recommendation |
|---|---|
| Venting | Through window or wall plate, short exhaust run, slight downward slope outward. |
| Combustion air | Optionally route intake outside to reduce drafts. |
| CO detection | Install CO alarm in garage (and in adjacent house if attached). Alarm primarily monitors heater venting integrity; brief car operation with normal ventilation will not trigger it. Avoid extended vehicle idling in sealed conditions regardless. |
| Fire safety | Keep a class B/C extinguisher accessible. |
| Power | Each unit draws ~10–15 W running, ~120 W start-up; can run from 12 V battery or UPS. |
| Fuel | ~0.2–0.3 L /hr (0.07 gal/hr); 5 gal ≈ 20–30 hrs continuous. |
| Maintenance | Run monthly at full output to prevent soot buildup. |
| Fuel quality | Use clean diesel, #1 diesel, or K-1 kerosene with stabilizer for clean burn. |
🪟 Heater Mounting & Window Insert Details
Window Insert Construction
- Panel material: Cut a 1/4–1/2 in fiber-cement sheet sized to the operable window opening. Options: HardieBacker 1/4” Cement Board, USG Durock 1/4” Cement Board, or thicker WonderBoard Lite 1/2”. All three products are fiber-cement (ASTM E136 noncombustible) with no paper facer, so they will not ignite even if the exhaust collar runs hot. HardieBacker does not publish a specific max temperature, but its hearth/wood-stove listing confirms suitability for this application. Thicker board adds stiffness. Do not use particle board, plywood, or other wood products — exhaust gas runs 200–300 °C (≈390–570 °F) with spikes up to 400–500 °C (≈750–930 °F) near the heater outlet, and prolonged heat exposure causes pyrolysis in wood products, lowering their ignition point over time. A scrap piece of sheet metal or aluminum is an acceptable alternative if cement board is unavailable.
- Insert construction: Sandwich the cement board inside a simple wood or aluminum frame, add foam weather stripping against the window jamb, and secure with screws or cam locks so the insert is airtight yet removable.
- Exhaust pass-throughs: Drill two holes (24mm) for the exhaust tubes. Install the VTurboWay 316 SS Thru-Hull Exhaust Skin Fittings (24mm, straight) using the included stainless screws and gaskets. These marine-grade fittings feature a double-wall design that isolates heat from the mounting surface and are purpose-built for diesel parking heaters (compatible with Webasto, Planar, Eberspacher, and Chinese diesel heaters including VEVOR). No additional sealants, furnace cement, or stove pipe sections are required — the fittings provide a clean, flanged, gasketed pass-through.
- Intake pass-throughs: Drill two additional holes for combustion air intake tubes. Intake air runs at ambient temperature, so thru-hull fittings are not required — a simple rubber grommet or weatherstripped hole is sufficient. Space intake and exhaust openings apart on the outside so exhaust is not recirculated into the intake.
- Serviceability: Label the insert and hoses for quick removal when permanent HVAC is online; store the panel for future emergency use.
- Spare exhaust extension: Keep the 10 ft stainless extension in reserve. The shorter factory pipe minimizes restriction for the window insert, but the longer section is ready if the exhaust needs to shift later (e.g., higher wall exit, routing around obstructions, or moving a heater outdoors temporarily) and also helps reduce noise/hot blast near doors.
Exhaust Routing (Per Heater)
VEVOR exhaust port → pipe (~1 ft) → muffler → pipe (~1-2 ft) → thru-hull fitting → outside
Use the included muffler. The heaters are inside the workspace, and even though exhaust exits outside, the pipe transmits vibration and drone noise back into the garage. The muffler eliminates this with negligible restriction on a short run.
Routing guidelines:
- Keep the total run short — a few feet from heater to thru-hull. Shorter = less restriction, less condensation, better draft.
- Mount the muffler close to the heater — within 1–2 ft of the exhaust port.
- Maintain a slight downward slope the entire way toward the thru-hull so condensation drains outside, never back toward the heater.
- Muffler clearance — it gets hot. Keep it off the floor and away from combustible materials. A simple metal bracket or strap to a wall stud works.
- Clamp every connection — every pipe-to-muffler and pipe-to-heater joint needs a stainless hose clamp tightened down. Each joint is a potential CO leak point.
- Extend pipe 2–3 inches past the thru-hull on the outside so exhaust drafts away from the building, not back against the wall.
Intake Routing (Per Heater)
VEVOR intake port → pipe → grommet/pass-through → outside
No muffler needed on intake — it pulls ambient combustion air only. Keep intake runs short and ensure the outside intake and exhaust openings are spaced apart.
Safety Check Before First Run
- All hose clamps tight at every exhaust joint
- CO alarm installed inside the garage
- Run both heaters at full output for 10–15 min
- Check every joint for heat or exhaust smell
- Verify exhaust is exiting cleanly outside (no smoke coming back in)
- Confirm intake is not recirculating exhaust
Materials List
| Item | Status | Est. Cost |
|---|---|---|
| 2× VTurboWay 316 SS Thru-Hull Fittings (24mm, straight) | ✅ Ordered | — |
| 1× Cement board sheet (3’×5’, 1/4”–1/2”) | Needed | ~$10–15 |
| Scrap wood or aluminum for insert frame | Check scrap pile | Free |
| Foam weatherstripping for window jamb | Needed | ~$5 |
| 2× Rubber grommets or weatherstripped pass-throughs (intake) | Needed | ~$5 |
| Total remaining materials | ~$20–25 |
This setup keeps both heaters protected indoors, maintains clean combustion air and safe exhaust routing, and avoids pressurizing the garage with outside-mounted units.
✅ Bottom Line
- Two 8 kW VEVOR heaters = workable solution for an uninsulated 24 × 40 ft garage in Michigan winter.
- Expect 40–55 °F interior temps in typical cold weather with minimal air sealing.
- Add temporary insulation and a small electric spot heater for comfort in sub-zero conditions.
- Once the garage is insulated and the boiler/mini-splits are installed, these VEVOR units will make excellent emergency backup heat sources for both garage and house. See Emergency House Heating Plan for the whole-house backup heating strategy and validation test plan.
📋 Related Documentation
- Winter Construction Strategy: Winter Construction Strategy — Comprehensive analysis of construction sequencing options and boiler installation timeline
- Permanent HVAC System: HVAC Strategy — Mini-split and radiant floor permanent system design
- Mechanical Room Build: Mechanical Room — Boiler installation location and dependencies
- Electrical Planning: Electrical Planning — Electrical service requirements for boiler operation
- Project Timeline: Timeline — Projected milestones for electrical service, gas service, and boiler installation
Last updated: February 2026 Author: Dan Gahagan — Garage Project Notes