Sunroom Heaters: How to Heat a Sunroom in the Cold Winter

A sunroom is a versatile space that allows homeowners to enjoy natural light and outdoor views while being sheltered from the elements. However, during the cold season, a sunroom can quickly become an uninviting space if it isn’t properly heated. 

In this guide, we discuss how to heat a sunroom during cold weather, and explore the different types of sunroom heaters.

Why Do You Need to Heat a Sunroom?

Sunrooms are primarily constructed with glass to allow natural light, featuring large windows, glass walls, or even glass ceilings. Unlike the rest of the home, sunrooms are often designed with large windows, less insulation, and lighter materials, making them particularly susceptible to temperature fluctuations. 

In particular, any form of windows are much less effective at reducing heat exchange than windowless walls. According to the US Department of Energy, the heat exchange through windows accounts for between 25–30% of residential heating and cooling.

An unheated sunroom may cause:

Discomfort: Without proper heating, a sunroom can become uncomfortably cold, making it unusable during the winter months. This defeats the purpose of having a sunroom, as it limits the ability to enjoy this space year-round.

Damage to furniture and flooring: Cold temperatures and moisture can warp furniture, flooring, and other decor in your sunroom. Materials like wood and fabric are particularly vulnerable to warping, cracking, and mold growth when exposed to fluctuating temperatures and humidity.

Higher utility bills: An unheated sunroom can act as a cold sink, drawing warmth away from adjacent rooms and forcing your heating system to work harder, leading to higher energy bills.

Structural issues: Prolonged exposure to cold and moisture can cause structural issues in your sunroom, such as cracks in the walls, window seals, and flooring. Over time, this can lead to costly repairs.

Types of Heaters for Sunrooms

When it comes to heating a sunroom, there are a wealth of options to consider. Each type of sunroom heater has its own pros and cons, depending on your specific needs and the design of your sunroom.

Portable Electric Space Heaters

Pros:

Ease of Use: Electric space heaters are portable, easy to set up, and can be moved to different areas as needed.

Affordability: They are generally inexpensive to purchase.

No Installation Required: Simply plug in and use.

Cons:

Limited Coverage: They are best suited for small areas and will struggle to heat a large sunroom effectively.

Energy Consumption: Electric space heaters can be energy-intensive, leading to higher electricity bills.

Safety Concerns: There is a risk of fire if not used properly, especially if placed near flammable materials.

Temporary: These heaters should only be used while you are in the space and should not be left to run when you are not present.

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Electric Baseboard Heaters

Pros:

Even Heat Distribution: Baseboard heaters provide consistent, even heating across the room.

Silent Operation: They are quiet and unobtrusive.

Low Maintenance: Baseboard heaters require minimal maintenance.

Cons:

Installation Required: They need to be installed along the base of the walls, which can be a drawback if your sunroom has limited wall space. They also require a dedicated power line.

Slow to Heat: Baseboard heaters can take longer to warm up a room compared to other heating options.

Recommended Baseboard Heater for Sunrooms:

King 4K2010BW 4 Foot 1000 Watt Electric Baseboard Heater

The King K-Series baseboard heaters are easy to install and attractive to look at, with a smooth, baked enamel, bright white finish and sleek rounded edges for safety. This 48″ long model uses 208V electricity and delivers 1000 watts of electric heat.

It uses crush-proof ribbon aluminum finning compression welded to the heating element to provide a chimney-type flue for maximum heat transfer. To protect the unit from overheating, it also comes with a SureStop high temperature-limit feature that shuts power off to the heater in an abnormal event.

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Packaged Terminal Air Conditioner (PTAC)

Pros:

Multi-function: PTACs can provide both heating and cooling functions in one package.

Targeted Heating: As a standalone unit, the PTAC operates independently of other heaters in the house.

Cons:

Installation: Requires placement on an exterior wall using a wall sleeve.

Space Consideration: PTACs sit close to the floor, requiring unobstructed space.

Recommended PTAC for Sunrooms:

Amana PTH153J50AXXX 15000 BTU Class 10.4 EER PTAC Air Conditioner with Heat Pump – R32

This PTAC offers 14,400 / 14,600 BTUs of cooling power, a 14,000 / 14,300 BTU heat pump and a 5.0 kW electric heater, providing approximately 14,000 / 17,100 BTUs of electric backup heat.

The new series are even quieter than previous Amana PTACs. The new, improved design reduces operating noises and features an STC (Sound Transmission Class) of 29, making it perfect for sunrooms that require peace and quiet. The new series also eliminates the user-operated control panel, giving it a sleeker appearance that matches sunrooms.

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Radiant Floor Heating

Pros:

Comfort: Radiant floor heating provides warmth from the ground up, creating a cozy and comfortable environment.

Even Heating: It ensures consistent warmth throughout the room without cold spots.

Invisible Heating: Since it’s installed under the floor, it doesn’t take up any visible space.

Cons:

Cost: Installation can be expensive, especially if retrofitted into an existing sunroom.

Installation Complexity: Requires professional installation and may involve significant renovation work.

Slow Response Time: It takes time to heat the room, as the warmth has to radiate through the floor.

Our Recommended Radiant Floor Heating System for Sunrooms:

Nuheat Electric Floor Heating Mat – 20 Ft. x 10 Ft. / 240 Volt

Nuheat Floor Heating Mats are easy to install and are available in just about any size you may need. Additional Nuheat Floor Mats can be added, if necessary, to get full sunroom coverage.

This particular 20 Foot floor mat is only available in 240 inches long by 120″ wide or 20 feet by 10 feet. Each square or rectangular floor mat can be laid in either direction. Nuheat floor mats are pre-wired and cannot be cut, but they can be laid in either direction so if the width and length don’t match your needs, you can turn it.

They can be installed under tile, stone, marble, laminate or engineered wood floors.

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Ductless Mini-Split Heat Pumps

Pros:

Energy Efficiency: Ductless mini-splits are highly energy-efficient and can provide both heating and cooling.

Zoned Heating: They allow you to control the temperature in the sunroom independently of the rest of the house.

Low Operating Costs: While the upfront cost is higher, they are economical to run.

Cons:

Installation Cost: Requires professional installation, which can be costly.

Aesthetic Impact: The indoor unit is visible on the wall, which may not suit everyone’s aesthetic preferences.

Recommended Mini-Split Heat Pump for Sunrooms:

Friedrich FSHW121A 12000 BTU, 18.0 SEER2 Floating Air Select Series Single Zone Mini Split – Heat and Cool – 115V – R32 Refrigerant

This single zone mini split is a 115 Volt, cooling with heat pump system. It features high efficiency ratings including a 18.0 SEER2 and 10.2 EER2. The built-in low ambient cooling capabilities will cool your space when outside temperatures are as low as 5°F. 

The 12,000 BTU heat pump will work hard to keep your sunroom warm. It can provide 8,800 BTUs at 17°F but with its low ambient heating capacity, will provide heat even with temperatures down to -4°F! The system’s 9,000 BTUs will also cool a sunroom that is about 450 sq. ft.

What’s more, it’s also Smart Home Ready with built-in WiFi and access to FriedrichGo App for wireless control as well as Google Assistant and Alexa voice commands

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Ventless Gas Heaters

Pros:

Ease of Installation: Ventless heaters are easier and cheaper to install since they don’t require a venting system. This makes them ideal for sunrooms where venting might be a challenge.

Lower Initial Cost: Ventless heaters are generally less expensive both in terms of purchase price and installation.

Flexibility: These heaters can be installed almost anywhere, as they don’t need to be placed near an exterior wall for venting.

Compact Design: Many ventless models are smaller and more compact.

Cons:

Safety: Ventless heaters exhaust combustion gases into the sunroom. Proper safety measures, including carbon monoxide detectors, are essential.

Moisture Issues: Ventless heaters release water vapor as a byproduct, which can increase humidity levels in the sunroom.

Air Quality: The lack of venting means any combustion byproducts remain in the sunroom, which could affect indoor air quality over time.

Regulations: Ventless heaters are restricted in some areas, so you’ll need to check local building codes before purchasing.

Recommended Ventless Gas Heater for Sunrooms:

Empire Comfort Systems BF-30W 30,000 BTU Blue Flame Vent-Free Gas Heater with Thermostat

The BF-30 comes with a hydraulic thermostat and modulates from 8,500 BTUs to 30,000 BTUs for continuous temperature control. The heater cycles the main burner flame from HI to LO so that when the thermostat is satisfied, to OFF while still leaving the pilot on. This reduces the large flame to a smaller flame while still emitting heat.

It has 99.9% AFUE Efficiency Rating and includes an Oxygen-Depletion Sensor that shuts off the unit if there is not enough available fresh air in the sunroom.

This model is available in Natural Gas and Liquid Propane versions.

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Vented Gas Heaters

Pros:

Safety: Vented heaters are safer because they draw combustion air from outside and exhaust the gases directly outdoors. This minimizes the risk of carbon monoxide buildup and maintains indoor air quality.

Efficiency: They are more efficient since they use outdoor air for combustion, reducing heat loss and maximizing energy use.

Moisture Control: Since the exhaust is vented outside, direct vent heaters do not add moisture to the indoor air.

Higher Output: Vent heaters are more powerful, making them better for larger spaces or for sunrooms with higher heating demands.

Cons:

Installation Complexity: The vent system requires venting through an exterior wall or roof, which can be more complicated and costly, especially in glass-filled sunrooms.

Higher Initial Cost: The unit cost and installation for direct vent heaters are typically higher than ventless models.

Aesthetic Impact: The venting system can affect the interior and exterior aesthetics of the sunroom.

Recommended Vented Gas Heater for Sunrooms:

Rinnai EX38DT 38400 BTU EnergySaver Direct Vent Wall Furnace

This direct-vent wall furnace is capable of 38,400 BTUs of heat output, making it ideal for large sunrooms or those located in cold weather regions. It features modulating technology to optimize the efficiency of the unit. This allows it to provide just the right amount of heat at any given moment, by constantly monitoring the room temperature and detecting temperature fluctuations.

A built-in, programmable thermostat is located on top of the unit of the EX38DT. It has 2 timer settings and can be connected to a WiFi enabled thermostat giving you more flexibility in your comfort control when you are away from home or just in a different room! And, don’t worry if there is a power failure while your system is on, the appliance will shut off the gas and once power is restored, this unit will restart automatically.

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Tips to Improve Heat Retention in a Sunroom 

✔ Insulate Windows and Doors

Install thermal curtains, window film, or weather stripping to reduce heat loss through windows and doors.

✔ Use Rugs and Carpets

Adding rugs or carpets can help retain heat and prevent cold from radiating through the floor.

✔ Seal Cracks and Gaps

Ensure that all cracks, gaps, and leaks are sealed to prevent drafts and heat loss.

✔ Install a Ceiling Fan with Reverse Function

Ceiling fans with a reverse function can help circulate warm air that rises to the ceiling back down to the living area.

✔ Add Thermal Blinds or Shades

These can help trap heat during the day and prevent it from escaping at night. According to the Department of Energy, properly installed cellular shades can reduce heat loss through windows by 40% or more, which can shave up to 10% off your heating costs.

✔ Incorporate Insulated Roofing Panels

If possible, consider upgrading the roof with insulated panels to improve overall heat retention.

✔ Maximize Sun Exposure

Keep windows clean and free of obstructions to maximize the amount of sunlight entering the room during the day.

✔ Add a Heat Reflector

Placing a heat reflector behind radiators or heaters can help direct more heat into the room rather than letting it escape through the walls.

By carefully selecting the right heating method and implementing these heat retention strategies, you can enjoy a warm and comfortable sunroom throughout the cold season, making the most of this beautiful space year-round.