Do you ever feel an uncomfortable chill near your supply vents (air vents) in winter? Many people struggle with rooms that don't warm up despite the heating being on, or a sensation of cold air coming from the supply vents.

The reason for cold supply vents lies in the ventilation system and installation environment. By understanding the cause correctly, you can often alleviate the cold with simple methods without unnecessarily increasing heating costs.

This article clearly explains why supply vents are cold, and provides solutions for the vents themselves and for keeping the entire room warm. Use these tips to find methods that suit your living environment and make your winter a little more comfortable.

Why are supply vents cold? Their mechanism and main causes

"My room won't warm up even with the heater on," or "I feel a cold draft near the supply vent." When this happens, it's difficult to find an effective solution without knowing the cause. Let's first look at the mechanism that makes supply vents feel cold.

The basic role of supply vents (air vents)

Supply vents are openings designed to bring outside air into a room. These are typically small holes or covers installed in walls.

While exhaust vents (such as extractor fans) are responsible for expelling stale indoor air outside, supply vents bring fresh outdoor air into the room. These two components work together to ensure indoor air circulation.

Since supply vents are always connected to the outside, cold air can easily enter in winter when the outdoor temperature drops. The sensation of "the area around the supply vent being cold" can be considered a natural phenomenon due to its structure.

The mechanism of cold air entering (what is cold draft)

The phenomenon known as "cold draft" is often behind the particularly cold feeling around supply vents in winter.

Cold draft is the phenomenon where air that has been cooled by contact with cold surfaces like windows or walls flows downwards towards the floor. Outside air entering through the supply vent cools the interior wall surfaces, and this cold air then flows downwards, making the floor and areas near the floor feel colder.

This cold draft is often the reason why your feet feel cold even when the heating is on, and it's characterized by contributing to a perceived coldness even if the supply vent is located high up.

Relationship with 24-hour ventilation

Since the revision of the Building Standards Act in 2003, the installation of 24-hour ventilation systems has been mandatory in all homes. This is to prevent health problems (sick building syndrome) caused by chemical substances (such as formaldehyde) emitted from building materials.

24-hour ventilation systems are designed to replace more than half of the indoor air per hour. "Type 3 ventilation" is a commonly adopted method in general housing, where air is exhausted mechanically (by a fan) while fresh outdoor air is naturally drawn in through supply vents.

While this method has low installation costs and is easy to maintain, its drawback is that, due to its structure, which draws in outdoor air as is, areas around supply vents tend to become cold in winter.

Reasons why you shouldn't close supply vents

Many people think, "If it's cold, just close the supply vent." However, completely closing the supply vent is not recommended.

If you block the supply vent, the indoor ventilation will not function properly. As a result, the following problems are likely to occur:

• Chemical substances in the air, such as formaldehyde, will accumulate, increasing the risk of sick building syndrome.
• Humidity will build up, making condensation and mold more likely to occur.
• Carbon dioxide levels will rise, which can lead to headaches and fatigue.

Stopping ventilation simply because "it's cold" poses risks to both your health and your home. The key is to keep the supply vents open and address the cold through other methods.

Measures to try when your supply vents are cold

To alleviate the cold without closing the supply vents, it's effective to combine several methods. Try them in order, starting with the easiest ones.

Installing supply vent filters

One of the easiest and most effective ways to combat cold supply vents is to install filters.

Supply vent filters moderately temper the airflow, preventing a sudden rush of cold air into the room. Since they don't completely block the air, they alleviate cold without impairing ventilation functionality.

Most products can be installed without tools, making them easy to introduce even in rental properties. It's worth trying this method as a first step in combating the cold.

Utilizing supply vent covers and insulating sheets

Another option is to attach a dedicated cover to the supply vent. Installing a cover changes the flow of outside air directly blowing into the room, which helps reduce the intensity of cold air hitting your body.

Especially for "full-opening type" supply vents (those where air enters from all sides – top, bottom, left, and right), the perceived temperature tends to drop more, so the airflow regulating effect of a cover will likely be noticeable. When choosing, it's important to select a type that leaves about 1/3 to 1/2 of the opening exposed so as not to hinder ventilation.

Even applying a thin cloth or insulating sheet to part of the supply vent can have some effect. Trying out items you already have before purchasing a specialized cover can be a good approach.

Adjusting supply vent airflow

Some types of supply vents allow for adjustment of their opening (degree of opening). If your supply vent has a lever or slide adjustment function, you can reduce the amount of cold air flowing in by narrowing the opening.

However, it's important to always keep it slightly open to prevent insufficient ventilation. A practical approach would be to keep it fully open during the day and only narrow the opening during times when you particularly notice the cold, such as before bedtime.

If you're unsure which type of supply vent you have, try removing the cover and checking the internal structure.

Cold対策 using supply vent filters and how to choose them

Among the available solutions, filters are an easy-to-adopt method as they can improve coldness without hindering ventilation. Let's delve deeper into the effectiveness of filters and key points for choosing them.

How filters change the way cold air enters

Without a filter, outside air flows directly and unimpeded into the room. The significant difference with a filter is that it creates resistance to the airflow, causing the cold air to enter with less force.

Even with the same outdoor temperature, the perceived temperature changes depending on whether air directly hits your body. Similar to how "air conditioning directly hitting your body makes you feel cold," simply reducing the air velocity can significantly alleviate discomfort.

While it doesn't completely block cold air, many people find that it makes sitting near the supply vent less bothersome.

Why antibacterial and pollen control can be achieved simultaneously

Supply vent filters not only help with cold prevention but also improve the indoor air quality. This is because filters can block a certain amount of dust, pollen, PM2.5, and other fine particles attempting to enter from outside.

Specifically, choosing filters with antibacterial and antiviral properties can also help suppress the growth of bacteria and viruses in the air. "Air King" filter specialty store offers ventilation and supply vent filters coated with "AT254," which boasts 99.88% antibacterial and antiviral performance, making it easy to achieve both cold protection and air quality improvement simultaneously.

For those concerned about hay fever or allergies, or households with small children or the elderly, installing filters will yield even greater benefits.

How to choose filters and目安 for replacement timing

When choosing a supply vent filter, you first need to check the size and shape of your home's supply vent. Supply vents come in various shapes such as square, circular, or donut-shaped, and if you don't choose a filter that matches the shape, it may not be installed correctly.

The general guideline for replacement is every 2-3 months, but in areas near roads or with high pollen counts, dirt accumulation may accelerate. If the filter appears discolored or if you feel the airflow has weakened, it's likely a sign to replace it.

"Air King" offers over 167 types of filters for various shapes, providing a wide selection to easily find a size that fits your home's supply vent. If you're unsure about choosing the right size, please feel free to consult us.

▶︎Click here for a list of ventilation and supply vent filters

 

Measures to improve overall room warmth

By combining measures for the supply vents with efforts to improve the overall warmth of the room, you can make your living space even more comfortable. We will introduce methods to suppress the effects of cold air while increasing heating efficiency.

How to seal drafts from windows and doors

Cold rooms aren't solely caused by supply vents. Drafts entering through window sashes and door gaps are also a major factor in lowering the perceived temperature.

For window gaps, simply applying commercially available gap tape can block a certain amount of cold air infiltration. Applying insulating film to window panes can also be expected to reduce the transmission of cold from the glass surface.

A significant amount of indoor warmth is said to escape through windows, so switching to thick curtains or insulating curtains can also improve heating efficiency. Combining this with measures for supply vents can further enhance the overall insulation of the room.

Circulating warm air with a circulator

Warm air tends to rise to the ceiling, while cold air sinks to the floor. If you feel cold at your feet even with the heating on, this temperature unevenness is often the cause.

By using a circulator to circulate the air in the room, you can bring the warm air near the ceiling down to the floor. Effective usage involves placing it diagonally across the room and directing the airflow towards the ceiling, or aligning it in the same direction as the air conditioner to create airflow.

Even cold air entering from the supply vent will mix more easily with warm air as the entire room's air circulates, helping to alleviate localized coldness.

Counteracting cold floors with insulation goods

Cold transferred from flooring or cold tile surfaces also contributes to discomfort in winter. Cold air from the floor not only lowers the perceived temperature but also dulls the effectiveness of heating.

By laying down rugs or insulating mats, you can physically block the cold from the floor. Especially cork mats and insulating sheets have high heat retention, and simply placing them on the floor can alleviate coldness at your feet.

The floor near windows is one of the places where cold air accumulates the most, so installing insulating panels or gap tape under windows is also effective. By combining several easy-to-use goods, gradually improve the overall warmth of your room.

Frequently asked questions about cold supply vents

Here are common questions regarding cold supply vents. Please check these points before considering solutions.

Is it okay to block supply vents?

Completely blocking supply vents is not recommended. Supply vents function as part of a 24-hour ventilation system, and blocking them will result in insufficient indoor ventilation. This can lead to the accumulation of chemical substances like formaldehyde, as well as an increased risk of mold and condensation due to trapped humidity.

If the cold is a significant concern, try controlling the inflow of cold air by adjusting the opening, or using filters or covers, instead of completely blocking the vent.

Can I implement cold weather countermeasures for supply vents even in a rental property?

Many measures can be taken even in rental properties. Most supply vent filters can be installed without tools, making them easy to use in properties where restoration to original condition is required upon moving out. Some attachable covers can also be installed without drilling holes in the wall, as they use double-sided tape.

Window insulating film, gap tape, and insulating curtains are also items that can be easily restored to their original condition. It's a good idea to check in advance whether the products you plan to use are suitable for rental properties.

Where can I buy supply vent filters?

When choosing a supply vent filter, you first need to check the size and shape of your home's supply vent. Supply vents come in various shapes such as square, circular, or donut-shaped, and if you don't choose a filter that matches the shape, it may not be installed correctly.

The general guideline for replacement is every 2-3 months, but in areas near roads or with high pollen counts, dirt accumulation may accelerate. If the filter appears discolored or if you feel the airflow has weakened, it's likely a sign to replace it.

"Air King" ventilation and supply vent filters are products designed by house cleaning professionals who thoroughly understand dirt and grime. They are structured to allow air to pass through while catching dust and dirt, and they are made without glass fiber materials, ensuring consideration for everyday use.

With over 167 types available for various shapes, there is also a system to find the right filter based on your current supply vent's shape or product number. If you are unsure about size selection, you can consult our expert staff.

▶︎Click here for a list of ventilation and supply vent filters

 

Summary | Understand the cause of cold supply vents and take appropriate measures

The main reason supply vents feel cold is due to the mechanism of 24-hour ventilation systems. Especially in homes with Type 3 ventilation, where outside air flows directly into the supply vents, cold drafts are common in winter. Blocking supply vents because it's cold can lead to insufficient ventilation, posing risks to health and the home. Therefore, it's crucial to keep them open while implementing countermeasures.

A simple and cost-effective solution is to install filters on supply vents. They gently temper the inflow of cold air while also blocking dust and pollen, simultaneously addressing cold and improving indoor air quality. Combining multiple measures such as using covers, adjusting airflow, and improving overall room insulation and warm air circulation can lead to even greater effectiveness.

When choosing a supply vent filter, the first step is to check the shape and size of your home's supply vent. Selecting a product that matches the shape ensures effective cold prevention without hindering ventilation. At "Air King," you can find filters based on shape and product number, so start by checking the shape of your home's supply vent.