Steps To Prepare A New Hampshire Greenhouse For Winter Storms

A New Hampshire winter can bring heavy snow, driving wind, freezing rain, and prolonged cold. Preparing a greenhouse for this season requires a systematic approach that protects structure, plants, and equipment while minimizing the risk of catastrophic failure during a storm. This guide provides concrete, actionable steps, practical takeaways, and realistic preparations tailored to the climate and likely hazards in New Hampshire.

Understand the Risks and Local Conditions

New Hampshire winters vary by region. Coastal areas may experience more freezing rain and wind, while higher elevations see deeper snow and longer cold spells. Before you begin winterizing, assess the local risks you are likely to face.

• Snow accumulation and drifting that increases roof load.
• Freezing temperatures that threaten pipes, tanks, and sensitive plants.
• Wind-driven damage to framing, glazing, and seals.
• Ice buildup on gutters, eaves, and entrance areas.
• Power outages that interrupt heat, ventilation, and monitoring systems.

Recognize how these conditions affect your particular greenhouse type: glass, polycarbonate, or polyethylene hoop houses each behave differently under snow and wind.

Inspect Structure and Make Repairs

A rigorous inspection and repair cycle is the first and most cost-effective defense.

• Check framing for rot, rust, cracks, bent members, and loose fasteners.
• Examine glazing or covering: look for cracked glass, delaminated polycarbonate, punctures in film, and loose seals.
• Inspect doors, vents, and seals; replace worn gaskets and weather stripping.
• Verify anchor points and foundation connections to ensure the greenhouse resists uplift and drift pressure.

If you find marginal members or attachments, reinforce them now. Add diagonal bracing to walls and roof where wind loads are a concern. Replace or retension polyethylene film in hoop houses rather than postponing — loose film will pound and tear in a storm.

Strengthen Snow Load Resistance

Snow load is one of the most important threats. Snow sitting on the roof increases static load and can lead to collapse if the structure is under-rated.

• Remove snow promptly during and after storms to prevent excessive accumulation.
• Use roof rakes with long handles or poly roof rakes that will not damage glazing.
• For hoop houses, maintain a pitch steep enough to encourage snow slippage. If pitch is shallow, consider temporary supports to reduce span and deflection.
• Reinforce rafters with collar ties or additional purlins to reduce unsupported spans.
• Check manufacturer-rated snow loads and do not exceed them; if uncertain, consult a structural engineer for high-value greenhouses.

Practical takeaway: plan to remove snow when accumulations exceed 4 to 6 inches on shallow or older structures; for steep-pitch and well-supported greenhouses the tolerance is higher.

Insulate and Reduce Heat Loss

Reducing heat loss lowers the required heating energy and makes surviving a power outage easier.

• Add bubble wrap insulation to glazing. Two layers of 6mm horticultural bubble wrap can dramatically reduce radiant and convective heat loss while allowing light transmission.
• Install a thermal curtain or night insulation that can be pulled across the greenhouse at night.
• Seal gaps around doors, vents, and unions with weather stripping and closed-cell foam tape.
• Consider interior storm panels for glasshouses during the coldest months.

Practical takeaway: even simple, low-cost insulation measures reduce heater run-time and can prevent critical temperature dips during short outages.

Plan Heating and Fuel Reserves

Heating is central. Decide on heating strategies based on available fuel, greenhouse size, and reliability requirements.

• Choose a primary heater that matches the greenhouse volume and desired temperature. For critical crops and continuous operation, choose a reliable fuel source (propane, natural gas, or electric) and maintain proper exhaust and CO monitoring.
• Provide backup heating options: a secondary portable heater or an insulated thermal battery (water barrels) that stores heat from daytime heaters or passive solar.
• Keep adequate fuel on hand. Do not wait until a storm approaches to refill propane or oil tanks.
• For larger operations, install dual-fuel capabilities or automated transfer switches so you can switch heat sources if one fails.

Safety note: never operate unvented combustion heaters in an occupied greenhouse without adequate ventilation and CO detectors.

Protect Water Systems and Irrigation

Water lines that freeze will disrupt plant care and can burst, causing hidden damage.

• Locate pumps, sensors, and filters inside insulated areas or wrap them with heat tape rated for outdoor use and protect with insulation.
• Use submersible, insulated tanks as water reservoirs inside the greenhouse; water mass buffers temperature swings and provides heat when heated indirectly.
• Install frost-proof hydrants or keep hoses and spigots clear of wind-exposed areas.
• Drain or blow out external irrigation lines if they are not in use.

Practical takeaway: moving critical water infrastructure inside the heated envelope is a simple, effective safeguard.

Arrange Ventilation and Humidity Control

Cold winters reduce the need for ventilation but create condensation and humidity issues that foster disease.

• Use intermittent ventilation during warmed daytime hours to manage humidity and reduce mold risk.
• Install circulation fans to prevent cold pockets and reduce the chance of local frost forming on plant tissues.
• Use dehumidifiers in high-value operations or manage humidity through heating and controlled ventilation schedules.
• Keep gutters and downspouts clear to prevent ice dams that block drainage and create localized melting and refreezing.

Prepare Plants and Crop Management

Not all plants are equal. Sort, protect, or move plants according to cold tolerance and value.

• Move the most sensitive and valuable plants to the warmest sections (near heaters, interior benches, or against thermal walls).
• Group plants by temperature requirement; this reduces heating zones and eases monitoring.
• Use individual plant covers, row covers, and cold frames for extra protection on the coldest nights.
• Prune only when necessary; open wounds freeze more easily and slow healing. Instead, focus on reducing stress and ensuring steady moisture.

Practical takeaway: a small, well-maintained inner area for high-value plants is more manageable than heating the whole greenhouse to the same level.

Power Backup and Monitoring

Power outages during storms are common. Plan for redundancy and remote monitoring.

• Install a generator sized to run essential systems: critical heaters, fans, and monitoring equipment. Calculate required capacity by summing wattage of devices and include a safety margin.
• Use automatic transfer switches to start backup systems without manual intervention.
• Put thermostats, CO detectors, and temperature sensors on battery-backed or UPS power, and consider cellular or battery-powered remote monitoring so you can check conditions when off-site.
• Keep spare batteries, fuses, and a basic tool kit accessible.

Practical takeaway: a modest generator dedicated to heat and circulation can prevent crop loss during short outages.

Stock Supplies and Create an Emergency Plan

Have supplies and a plan ready so you can act quickly during a storm.

• Maintain an inventory of spare glazing, fasteners, sealant, poly film, bubble wrap, heat tape, hand tools, and tarps.
• Create a checklist and assign responsibilities if multiple people share greenhouse duties. Include steps for snow removal, heater restart, emergency plant relocation, and fuel procurement.
• Practice emergency drills and ensure safe access to the greenhouse during icy conditions.
• Keep written instructions near the greenhouse for any temporary workers or helpers.

Example emergency checklist:

• Batteries and backup power: charged and tested.
• Heater operational and fuel topped up.
• Snow removal tools available and accessible.
• Critical plants relocated and grouped.
• CO and temperature alarms verified.

Post-Storm Recovery and Analysis

After a storm, inspect thoroughly and learn from the event.

• Check structural integrity, glazing, seals, and anchors.
• Look for water intrusion, mold, or signs of freeze damage to plants.
• Repair damage immediately to prevent secondary failures.
• Record what worked and what failed. Adjust your winter plan and supplies accordingly.

Practical takeaway: quick, thorough post-event action limits long-term damage and prepares you for the next event.

Final Practical Takeaways

• Inspect, reinforce, and repair before the first heavy snow.
• Prioritize protection for the most sensitive structures, systems, and plants.
• Reduce heat loss through simple insulation like bubble wrap and thermal curtains.
• Keep reliable backup heat, power, and fuel on hand; a small generator plus basic heat source often prevents catastrophe.
• Protect water systems with internal placement, heat tape, and insulation.
• Keep snow removal tools ready and plan for regular roof clearing to avoid overloading the structure.
• Monitor remotely when possible and maintain an emergency checklist and supplies.

Winterizing a New Hampshire greenhouse is a mix of preventive maintenance, intelligent design choices, and pragmatic emergency planning. A deliberate program of inspection, reinforcement, insulation, prioritized heating, and reliable backup systems will significantly reduce risk, protect crops, and keep your greenhouse functional through the long New England winter.