Several factors can cause a bedroom to be warmer than the rest of an apartment. The most common reasons include poor insulation, direct sun exposure, lack of air circulation, heat generating appliances in the room, and body heat from sleeping occupants. Quick answers to common questions about a hot bedroom are:
– Adding insulation, windows, shades can reduce heat transfer into the bedroom.
– Running fans, opening windows improves air circulation and cools the room.
– Turning off electronics and using cooler running appliances reduces internal heat sources.
– Using lighter bedding and keeping the door open allows excess heat to escape.
Heat Transfer and Insulation
Heat flows naturally from warmer areas to cooler areas until an equilibrium is reached. The rate of heat transfer depends on the temperature difference and effectiveness of insulation. Bedrooms often become hot spots due to high rates of heat transfer into the room from warm outside air, sunlight, and internally from other rooms. Insulation acts as a thermal barrier, slowing the transfer of heat into the bedroom.
Poor Insulation in Walls, Windows and Doors
Lack of adequate insulation in walls, ceilings, windows and doors allows easy heat flow into the bedroom. Older buildings often have little to no insulation compared to modern construction standards. Newer insulation materials like spray foam and insulated vinyl panels greatly reduce heat conduction. Check for gaps and cracks around windows, doors, electrical outlets and baseboards that allow air infiltration from outside. Consider installing weatherstripping and caulk to seal gaps. Double pane windows with argon gas filling are also much better at stopping heat gain than single pane glass.
Sun Exposure Through Windows
Sunlight shining directly into a bedroom rapidly heats the air, surfaces and objects inside. South and west facing walls receive the most solar radiation during summer afternoons and evenings. Install blackout window shades to deflect sunlight before it passes through the glass into the interior space. Adjustable screens, awnings and solar window films are other effective options to reduce solar heat gain. Strategically placed trees and shrubs outside can also block excessive sun exposure on windows.
Conduction from Attic and Ceiling
Heat radiating through the roof is readily conducted into the top floor living space. This effect turns south facing attics into extremely hot zones during summer months. Adding insulation into the attic floor and roof rafters impedes heat transfer into the bedroom below. An insulating R-value of R-38 or higher in the attic is recommended for warm climates. Ensure insulation forms a continuous barrier with no gaps or compression.
Lack of Insulation in Interior Walls
Bedrooms often share walls with living rooms, home offices and other rooms containing major heat sources. Televisions, computers, stoves and other appliances in adjacent rooms release significant thermal energy. Much of this warmth is passed through interior walls into the bedroom if insulation is missing. In older homes, installing insulation into wall cavities substantially slows this heat conduction process. Newer constructions utilize closed cell spray foam within the interior partitions.
Air Circulation and Ventilation
Restricted air flow prevents hot air from escaping the bedroom while fresh cooler air cannot enter. Running ceiling fans, opening windows and keeping the door ajar are simple ways to improve air circulation. The use of whole house and window exhaust fans accelerates hot air removal.
Keeping Windows and Doors Closed
The natural tendency is to keep bedroom doors and windows shut for privacy. However, this isolates the bedroom and blocks air exchange with the rest of the house. Hot stale air becomes trapped inside the room with no way to escape. Keeping the bedroom door open allows warm interior air to circulate out to cooler areas of the home. Opening windows enables cross breezes to develop, flushing out hot stagnant indoor air.
Lack of Air Circulation Within the Room
Standing fans rotate the air within a bedroom to avoid hot spots from developing. They work by evaporating sweat for a cooling effect while expelling heat build up along ceiling and walls. Fans placed in open doorways pull hot bedroom air into adjacent rooms. For improved air flow, position fans across from windows to push hot air outside. Ceiling fans circulating air in a downward direction also accelerate convective cooling as hot air rises.
Blocked Supply and Return Vents
Central heating and cooling systems rely on unobstructed supply and return vents to maintain comfort in bedrooms. Air filters should be changed monthly and vents kept free of furniture and bedding that restrict airflow. Return vents near the ceiling remove rising heat buildup. Supply vents usually located along the floor inject cooler conditioned air. Blocking these vents isolates the bedroom from the main HVAC system.
Lack of Exhaust Ventilation
Moisture released from occupants and their activities creates high humidity in the enclosed bedroom environment. This moisture retains heat. Opening windows helps lower indoor humidity levels by replacing moist interior air with drier outdoor air. Dedicated bathroom exhaust fans should be vented directly to the exterior when possible. Quiet but powerful whole house fans are also useful for purging hot indoor air on summer nights.
Poor Window Design for Cross Breezes
Fresh outside air only enters a bedroom if there are open windows on opposite walls to allow cross breezes. A bedroom with a single window or all windows on the same wall lacks sufficient ventilation. Ideally, windows should be operable with insect screens on every exterior wall to maximize cross flow. Casement or awning style windows with a full 90 degree opening provide far more airflow than small sliding windows.
Internal Heat Gains Within the Bedroom
Electronic devices, appliances and building materials inside the bedroom introduce substantial heat into the enclosed space. Overhead lighting, computers, televisions and other electronics operate less efficiently at higher temperatures, compounding the heat dissipated into the room.
Heat Emissions from Electronics
Televisions, gaming consoles, amplifiers, chargers and other electronics emit large amounts of infrared radiation and warm air into the immediate surroundings through normal operation. Flat screen TVs require extra ventilation to prevent overheating. Turn electronics completely off when not in use to eliminate this major heat source.
| Device | Typical Heat Output |
|---|---|
| Gaming console | 150 W |
| Desktop computer w/monitor | 400 W |
| 40″ flat screen TV | 150 W |
| Laptop computer | 20-60 W |
| Desktop external hard drive | 25 W |
Metabolic Heat Emissions from Occupants
The average person at rest releases 100 W of thermal energy into the surrounding environment through metabolic processes. During an 8 hour sleep cycle, one occupant adds 800 W-hrs of heat into a bedroom. The enclosed space with limited ventilation causes body heat to accumulate. Using lighter cotton bedding improves breathability and moisture wicking over thicker quilts. Sleeping nude or with minimal covering also reduces trapped body heat.
Inefficient and Overloaded Lighting
Conventional incandescent bulbs convert up to 90% of energy input into infrared heat rather than visible light. Large halogen torchieres popular in bedrooms have intense heat emissions. Replace outdated bulbs with LED equivalents to eliminate this internal heat source. Also avoid over-lighting the space with too many fixtures to reduce waste heat production.
Heat-Generating Appliances
Many bedrooms have televisions, mini-fridges, audio amplifiers and other appliances generating low-level heat. Small space heaters raising the room temperature should be avoided. Mini-fridges with freezer compartments operate less efficiently in hot environments. Unplugging or removing unnecessary appliances prevents excess heat build up. Modern TV designs dissipate heat better than older cathode ray tube technology.
Trapped Heat from Cooking
Bedrooms situated above a kitchen or near cooking appliances absorb convected heat through ceilings and walls. Running ventilation hoods while cooking and avoiding oven use during hot times of day reduces this effect. Light meals with minimal stove usage prevents the kitchen from becoming a heat source. Turn on whole house fans after cooking to purge rising hot air before it penetrates bedroom walls.
Optimal Thermostat Temperature Setting
A reasonable thermostat set point range for indoor cooling is 72°F to 78°F. Setting the temperature below 72°F encourages short cycling which decreases system efficiency. Allowing the home to exceed 78°F adds major heat into the interior. The optimal setback temperature when away is 85°F. Programmable and smart thermostats automatically adjust settings for energy savings.
Solutions to Reduce Unwanted Heat
The goal is to minimize heat transfer into the bedroom while maximizing ventilation and air flow. Here are some top methods to maintain a comfortably cool bedroom for sleeping.
Improve Insulation
Adding insulation reduces conducted and convected heat transfer, a major cause of hot bedrooms. Increase attic insulation to R-38 or higher to block roof heat penetration. Install full cavity wall insulation on exterior walls. Seal air leaks around windows and doors. Apply window film or install double pane windows to reflect solar gain.
Limit Sun Exposure
Blackout window shades mounted externally reflect up to 80% of solar radiation for superior heat blocking compared to interior shades. Solar screen mesh over windows diffuses harsh direct sunshine. Outdoor shade trees prevent the bedroom from heating in the first place. Tinting window glass reflects more sunlight as darker tints absorb less radiant energy.
Ventilate the Room
Use quiet high volume whole house fans mounted in walls to rapidly exchange air on summer nights. Install ceiling fans to circulate air and promote evaporation. Open windows on opposite walls to facilitate cross breezes. Keep the bedroom door open during the day to prevent hot isolated air. Ensure HVAC vents are unobstructed.
Reduce Internal Heat Sources
Turn off all lights and electronics when not needed. Swap incandescent bulbs for cool running LEDs. Unplug chargers and appliances to eliminate waste energy. Relocate heat generating electronics away from the bedroom. Cook early in the day and use ventilation to dispel rising kitchen heat.
Upgrade HVAC System
Ensure the central air conditioning unit is properly sized for the building. Installing ductwork in closed floor cavities instead of the attic prevents heat gain. Position the return air grill high on a wall to remove hot rising air. Set the thermostat between 72°-78°F and use a programmable schedule.
Conclusion
A bedroom may become excessively hot due to greater heat conduction through poor insulation, inadequate ventilation trapping hot air, and internal heat generation from appliances. Improve insulation in walls, attic and windows to reduce heat flow into the room. Ventilate through open windows, fans and exhaust systems. Eliminate unnecessary electronics and lighting. Reflect solar gains with shade screens and films. With proper design and some DIY upgrades, the bedroom can maintain a comfortable temperature for sleeping.