I would have thought good ventilation would bring much colder air in from the outside thereby mitigating the benefits of good insulation. How do modern houses deal with this issue or is good ventilation much less important and I expect? (I’m in the UK so we don’t have blown air heating/cooling as standard here)
In: Engineering
Ventilation is mainly recirculation. There is enough foot traffic in/out to refresh the air. No need to actively move outside air in and inside air out (larger commercial/residential buildings will do this depending on layout).
Insulation is about stopping heat moving through the walls/ceilings/floors/windows/doors. Keeping your heated/cooled air from physically leaving the living spaces is very important to that process. If you are actively venting your heated/cooled air outside you have to spend a lot of power to heat/cool the new air coming in.
Both play together. A simple example:
1. Bad Insulation and Bad Ventilation: Warm air that is inside heats up the insides, but that heat quickly escapes through the walls. The walls are cool and draw heat out of the room, on top of that, cold air keeps coming in, cooling everything even more.
2. Bad Insu, Good Venti: Warm Air (mostly) stays where it is supposed to be, and doesn’t flow out of the house, but the walls still drain heat from the rooms.
3. Good Insu, Bad Venti: The walls are not draining the heat out of the rooms, but any warm air is quickly pushed out by cold air. The insides may be reasonably warm, but there is still a cold draft of air going on and the room itself cannot maintain temperature without a heatsource.
4. Both good: Air only comes and goes where you want it to. You can fully control what goes where, and no heat is leaking out through the walls etc. It will always be as warm or as cold as you want it to.
Ventilation and Insulation are just tools to use to manage your houses temperature. Both together ensure that cold air only goes where you want it to (good ventilation) and any heat that you produce in a room will stay in that room (good insulation)
They have air handlers called energy/heat recovery ventilators ERV/HRV, that transfers the heat between the air coming in and out, to either keep more of the heat in or out depending on the season.
One way is a heat exchanger.
If you let two fluids com in contact with the same heat conducting object without mixing heat is transfered between them. The warmer fluid get coolare and the cooler get warmer. Optimalt they both reach the same temperature.
If the two fluids are the inside and outside air you have now heated the outside air a bit and save energy.
You can also use a heat pump that extract heat from the air you let out it use electricity but will be mor efficient compared to if you use outside air as the heat source.
This works in reverse too if the i side is cooler then the outside and you use a AC
In older homes it was believed that the “leaks” in a home will keep fresh air and air quality at reasonable levels, which also increased our costs to heat/cool our buildings. Many newer homes seal the house very well, required by laws on energy reduction, in all areas including around framing, windows and doors which was the cause of most old air leaks, “drafts”. When thus started to happen we found indoor air quality started to be an issue, sick building syndrome.
With all this in mind we needed to find a way to introduce fresh air into homes, that was not drastically causing us to loose energy in the form of heat. Equipment was modified/invented to help with this. We use items like heat recovery units (HRU), in ventilation systems. This allows some of the heat from the indoors to exchange with the heat from the fresh out doors, basically equaling the temperature of the fresh air coming in to the “old” air going out in a heat exchange medium. They keep the two air streams separate, but allow their heat to transfer. They save money, heating/cooling cost, while providing the fresh air you need in a house/building.
Nothing to do with “modern houses”, far more to do with just understanding what we’re doing.
My previous 1930’s UK house had double-brick-wall with a gap between, vent-bricks in staggered positions on both internal and external walls, and it worked perfectly fine. For decades people lived in that house with just a coal/log fire rising up one wall and were perfectly happy.
Then we got people who started sealing up bricks “because they let cold air in”, plasterboarding the entire interior, and so on. Now the house is warm, but full of damp and mould. So then they realise that they have to vent it, so they go to extraordinary lengths to vent it.
My current house is 1960’s. It’s tiny and they put a huge concrete-tile roof on it and pathetic insulation, plus breezeblock exterior walls and then everything else was plasterboarded inside. It wasn’t well designed, because it was originally council (social) housing and was always intended to have shared heating. I know, because the shared heating pipes were still in my loft and you can see where they ran through all three house’s lofts and then down into each house. They ripped them out in the 90’s I think.
What I did with both houses was insulate it, board out the loft, seal the house properly (yes, I know! But there was no ventilation by the time I bought either of them! There were however lots of gaps around windows, lots of open vents for things like tumble dryers, lot of loosely-exiting pipes, big gaps under the doors, and so on) and put in a loft positive pressure vent system (a big fan that slowly blows air down from the loft into the house).
Both houses instantly stopped being damp/mouldy and stay warm even with a constant “draught” from upstairs (you can get heated models that even heat the incoming air, but I don’t think they’re worth it). It’s just not flowing enough to hurt anything, all it’s doing it making sure you have a little fresh air. I still haven’t turned my heating on since February. It’s 20C in my living room, and 13C outside and has been all day. That basically doesn’t change until it drops below about 5C outside.
Ventilation and insulation are not the opposites of each other. You just have to have a balance. If you insulate like mad, it’s actually WORSE because then you HAVE to ventilate. If you ventilate like mad then it’s too cold and you lose all the heat you make. You have to have a balance, like everything else. Just like venting a bathroom – if you vent too much, it’s freezing, if you don’t vent enough the walls get sodden with water every time you have a shower and you end up with damp and other problems.
And the balance is really a tiny pathetic little fan blowing air constantly down from my loft (already warmed slightly by the house) back down into the house, and then sealing my house to make it almost airtight. Or some airbricks that aren’t obstructed. Or the heat recovery systems (but they are expensive and hard to fit yourself) which basically use the heat of “exiting” air to warm up “incoming” air that they put back into the house.
My house is basically always warm except when it’s -5C outside. Then I have to put the heating on (and I only have a tiny electric heater because I really don’t need more than that!). And I don’t have damp, mould, condensation etc. anywhere near what it was when I first moved into either house.
You can’t live in a hermetically sealed box (space stations and space craft have all kinds of moisture problems they have to have special equipment to deal with), and you don’t want to be letting all your heat out. You just need a balance. Which we used to understand in home design, then totally forgot for the sake of aesthetics or doing up and selling houses on quickly, and now we’re re-learning it with some proper tech.
Humans have lived in non-sealed, incompletely insulated dwellings for hundreds of thousands of years. Because they learned that completely sealing yourself in either kills you, makes you less healthy, or doesn’t actually make anything any better (e.g. water dripping off the walls with make you colder than a small draught in one particular part of the house that you can easily avoid).
Double-paned windows provide good insulation. Open them, if they’re well placed, and you get good ventilation.
Define “Good Ventilation”.
Using CO2 as a proxy for Indoor Air Quality, the goal is to have an indoor CO2 reading no more than 650 ppm above the outside reading. With OSA reading 420ppm, that’s 1070ppm for inside air. Depending on the air space and how many people are breathing, that doesn’t take many Air Changes per Hour (ACH) to meet that goal.
“a tight, well sealed newlyconstructed home usually achieves **.**6 air changes per hour or less. A reasonably tight, well constructed older home typically has an air change rate of about 1 per hour. A somewhat loose older home with no storm windows and caulk missing in spots has an air change rate of about 2. A fairly loose, drafty house with no caulk or weatherstripping and entrances used might have an air change rate as high as 4, and a very drafty, dilapidated house might have an air change rate of as high as 8.”
There’s a difference between what you want: “the cool clear air blowing across your face”, and what you need: “Given an average outdoor CO 2 concentration of 380 ppm, indoor CO2 levels should not exceed 1,035 ppm (380 ppm + 650 ppm = 1,030 ppm)”
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