I have tested three air vents in my home to see how they might help with reducing humidity. The test involved holding a hygrometer near the vents in question whilst they are open with air blowing in. Test done this morning. Dry day outside, albeit wet on the ground. Central heating off. Photos of vents below.
Baseline: mantlepiece in middle of dining room. 60% RH at 16.5C. No vent.
Wall vent near the floor of dining room, cover removed for test. 57% RH. Air blows through this vent quite strong and cold, which is why I sometimes cover it.
Vent at top of metal patio door in lounge. 63% RH.
Trickle vent at top of window in a bedroom. 63%
Limitations are that on my hygrometer, the thermometer is much slower to react than the humidity sensor.
Still, it seems to me that more humid air is being allowed in through the two trickle vents, contributing to more moist air in the home. Now these readings may be because the outside air is colder and therefore the RH higher... that air might be less moisture laden in absolute terms and will contribute to lower RH when warmed up inside. However, as mentioned above, the thermometer is slow on my device and didn't fall much near the open vents - this would mean the outside air would've shown a lower RH if it were holding less moisture. Another thought is that higher readings at higher up vents might not be moist air coming in but moist air from inside going out... impossible to say though, and if anything, felt like air was coming in.
This leads me to some questions:
- why does the lower wall vent, which lets in a torrent of outside air show a lower RH than the higher up trickle vents? I have noticed same before.
- do these vents allow in moist air and therefore contribute to higher humidity in the home in certain situations (assume a normal room, not a kitchen or bathroom with steam being created internally)?
- does the simple movement of air that these vents promote compensate for the fact that the air might be more moisture laden than the air inside the house? Where does that moisture go - my vents on different parts of house seem to have air coming in.
Obviously, there are air freshening benefits to the vents, I am only considering the humidity angle. Window manufacturers and others are recommending that trickle vents be left open at all times.
Thoughts?
Baseline: mantlepiece in middle of dining room. 60% RH at 16.5C. No vent.
Wall vent near the floor of dining room, cover removed for test. 57% RH. Air blows through this vent quite strong and cold, which is why I sometimes cover it.
Vent at top of metal patio door in lounge. 63% RH.
Trickle vent at top of window in a bedroom. 63%
Limitations are that on my hygrometer, the thermometer is much slower to react than the humidity sensor.
Still, it seems to me that more humid air is being allowed in through the two trickle vents, contributing to more moist air in the home. Now these readings may be because the outside air is colder and therefore the RH higher... that air might be less moisture laden in absolute terms and will contribute to lower RH when warmed up inside. However, as mentioned above, the thermometer is slow on my device and didn't fall much near the open vents - this would mean the outside air would've shown a lower RH if it were holding less moisture. Another thought is that higher readings at higher up vents might not be moist air coming in but moist air from inside going out... impossible to say though, and if anything, felt like air was coming in.
This leads me to some questions:
- why does the lower wall vent, which lets in a torrent of outside air show a lower RH than the higher up trickle vents? I have noticed same before.
- do these vents allow in moist air and therefore contribute to higher humidity in the home in certain situations (assume a normal room, not a kitchen or bathroom with steam being created internally)?
- does the simple movement of air that these vents promote compensate for the fact that the air might be more moisture laden than the air inside the house? Where does that moisture go - my vents on different parts of house seem to have air coming in.
Obviously, there are air freshening benefits to the vents, I am only considering the humidity angle. Window manufacturers and others are recommending that trickle vents be left open at all times.
Thoughts?
Attachments
Last edited:
