We changed our roof and cut CO2 emissions
martindaniel.co
martindaniel.co
Degree days work better in regression as, assuming the correct base temperature is chosen/calculated, heating degree days are directly proportional to heating energy consumption (including being zero when it is warm enough that no heating is needed) and cooling degree days are directly proportional to cooling energy consumption.
More info and data here: https://www.degreedays.net
including an article explaining the process typically used for before/after calculations:
https://www.degreedays.net/calculate-energy-savings
Disclaimer: I work for the company behind that site, and yeah I know it looks a bit dated :D
So buildings have what is known as a heating base temperature, which is the outside temperature above which heating is not needed inside the building. This is not the thermostat temperature inside the building (say 20 C), it is actually lower because of various factors like people and electrical equipment generating "free heat" inside the building, and how well the building is insulated to retain that free heat.
The base temperature varies from building to building, but let's say, for example, a fairly-well-insulated home might have a heating base temperature of 14 C. If the temperature outside is 14 C or above, that building will stay perfectly warm inside on its own, without the heating system needing to come on.
But, if the outside temperature drops below 14 C the building will need some heating to keep it comfortable inside. How much heating it needs will depend on how much the temperature drops below 14 C, and for how long.
And this is what heating degree days quantify. Here is an example diagram that demonstrates quite nicely how they are calculated (using a base temperature of 14 C):
https://www.degreedays.net/images/heating-degree-days-calcul...
The neat thing is that the heating degree days for any period of time represent all the relevant temperature variations across that period of time, and assuming you used an appropriate base temperature, are proportional to the heating energy consumption over that period of time. So for example you can have just one figure that represents the heating degree days across an entire week/month/year, and that will encapsulate all the relevant temperature variations across that week/month/year.
If January had 200 heating degree days, and February had 300, you can expect the heating energy consumption of the building to be 50% greater in February than in January. (Assuming you have chosen the right base temperature for your building that is!)
Compare this with knowing that the average temperature across a week/month/year was 12 C. What does that tell you about how much heating was needed in that week/month/year? Not a lot, cos you have no idea how much it varied within that time. This is the case even within a single day, since the temperature can vary a lot within a day.
Hence why people in the energy-saving business would typically use degree days rather than temperature data :)
(That said, hourly temperature data or similar is good for more sophisticated building simulations. But those are a lot more involved. On the simpler end of the spectrum degree days are a much better choice.)
If insulated well and air sealed a home would lose very little energy. But also you'd need a good air handling system to move and refresh the air.
I kinda feel sorry for the guy, investing all the hard work and having good intentions, but due to poor workman ship he cannot expect to get the insulating effects he's surely hoping for.
And therein is the rub! Ventilation is critical in building design and many older houses cannot easily be retrofitted with a mechanical ventilation system, not to mention the costs.
Also, sealing air gaps is pretty much impossible in a house that wasn't built this way. I have been trying all kinds of things in my (30 year old) house to seal up gaps but there are spaces inside the floors to the outside through small mortar gaps, spaces behind electrical sockets, gaps in various parts of the floor and even around windows between the finishing.
I would personally like to see a more top-level view from governments. In the UK, for instance, they should be targetting the oldest housing stock and simply replacing it. I know this is hard because people own their freeholds but if we are serious and if someone would get a nice warm house in return for their old house then I think most people would be up for it.
Is this a correct usage of amortization?
That spreading may come with its own costs, like interest, but that is not an essential component of amortization.
So to amortise the carbon cost we take the embodied carbon, plus the operation carbon over a time frame. If the operational carbon is negative we would expect that at some point it would break even.
So to help with the English, I don't think it makes sense to talk about the amortisation during the change over since that is just the embodied carbon. But I think it definitely makes sense to talk about the amortised cost over some other time period after the change over.
I live in a '30s UK semi detached. It had an air brick , a blocked up fire place and blown double glazing in each room. (barring two that were replaced)
We had to re-render the place, as it was starting to fall off at the front, and the back was scarred from unfinished renovations.
We replaced the double glazing with triple (it was cheaper than double glazing at the time, so a no brainer. has a u-value of about 1.0)
We also put 90mm of external wall insulation round the outside as part of the re-render. This cost an extra £4k compared to just a normal re-render.
before the insulation, in summer the front room would reach 37 degrees C with the blinds down, and in winter with a 5kw wood burner and central heating on full we'd reach about 18 degrees c when outside was either windy or -3c
Now in summer the hottest we've had it is about 29, with the blinds open. In winter we reach 20 within 30 minutes of the heating coming on. ( no need for the wood burner)
My parents also have a door to the attic for storage and heat leaks up through the un-insulated edge of the pull-down stairs door.
On YouTube Matt Risinger is a great resource for home repair and information. He tends to like expensive products but overall he explains main concepts well.
Early on, Risinger did a bunch "building science" explainer videos. Challenging then conventional building practices. Like advanced framing (using 2x6 studs at 24" spacing). Like properly insulate attics to prevent condensation and heat loss (keep HVAC vents within the thermal envelope).
Those early explainers are the foundation (harhar) of subsequent product and project highlights. Alas, now they're hard to find (via YouTube's lame UX). Risinger should probably pin primers to the top of his playlist, linking into his archive.
Having insulation on the outside of your structure, and especially outside of your air/vapour barrier, is ideally where you want it (behind whatever cladding you're using):
* https://www.buildingscience.com/documents/insights/bsi-001-t...
For us it stopped our moisture problem. We had mold growing on the walls, because all the moist air would hit the wall and dump out water (proper drops).
Now the walls are 10 degrees warmer, none of that condensation is built up.
there is also thermal mass and junk, but not having to wipe down the walls every night is a big big win
He does not go into much detail on roofs, but in his wall examples, the outer cladding and the drained cavity behind it appear to be a de-facto rain control barrier outside of the insulation layer (which could be, he says, rock wool or glass fiber, which are surely a big problem if they get wet, right?) If this is so, then what does it mean to say the insulation is outside of the rain control barrier? Furthermore, if we combine these diagrams with the one showing a roof-wall junction, there does not seem to be any barrier against rainwater reaching the wall insulation that way, and I cannot see how this is not a problem.
Yes, the cladding is acting as a bulk water control layer, but there is still moisture in the air from humidity.
* In a cold climate the warmer/moister inside air will at some point reach the edge of the building: by having the insulation on the outside of the control layer(s), the air will be kept warm, and so there won't be a cold surface for it condense on. If the insulation was on the inside then the control layer would be cold, where the air would condense, possibly causing mold growth.
* In a hot/humid climate the humid outside may get by the insulation and hit the cooler control layer and condense, but will just roll off the control layer outside of the building (and not cause mold inside).
> Furthermore, if we combine these diagrams with the one showing a roof-wall junction, there does not seem to be any barrier against rainwater reaching the wall insulation that way.
This is probably regarding Figure 5. All the various layers are connected to each other, so what's on the inside cannot get out, and what's on the outside cannot get in.
The black line (air/vapour layers) is continuous up the wall, around the corner, and onto the roof. The light blue (insulation) goes continuous up the wall, around the corner, and onto the roof. And the cladding is also continuous so that bulk water and UV rays are also blocked continuously.
See related articles:
> RR-0410: Vapor Barriers and Wall Design
* https://www.buildingscience.com/documents/reports/rr-0410-va...
> BSD-106: Understanding Vapor Barriers
* https://www.buildingscience.com/documents/digests/bsd-106-un...
With regard to their relative placement, see, for example, the caption to figure 2:
"Figure 2: "The Perfect Roof"—The perfect roof is sometime referred to as an “inverted roof” since the rainwater control layer is under the insulation and ballast." [my emphasis.]
The author also writes, in the caption to fig. 1: "The claddings function is principally to act as an ultra-violet screen", thus seeming to differentiate it from any of the control layers he listed at the start of the article.
In addition, the author also lists a separate item for air control, but later writes "What about this air control thing? Well air can carry a lot of water and water is bad for the structure" - further muddying the issue, as now he seems to be discussing water vapor.
I guess this could all be attributed to being sloppy about definitions, to the point of being unambiguously wrong when it comes to roofs.
The cladding can not stop any water and, if the control layers beneath the insulation are properly installed, it won't make any difference. The fact that the cladding does help in blocking rain is just a nice bonus to its primary function.
In some locations it may be difficult for the cladding to do this: think of any place very foggy. There's no way to make the cladding air tight, so high humidity (100%) air will get behind it (stopped by the c. layers). Or if you have shingles on your roof that leak (or get blown off in a storm), they can still block UV, but there will be dripping. And that's why you want the control layer(s) further in.
Water can destroy a structure very quickly if you don't allow for easy/quick drying. Defense in depth.
> In addition, the author also lists a separate item for air control, but later writes "What about this air control thing? Well air can carry a lot of water and water is bad for the structure" - further muddying the issue, as now he seems to be discussing water vapor.
At the top of the article he lists the control layers in order of importance. Controlling for air is more important than control for vapour, as this video explains:
* https://www.youtube.com/watch?v=FXXgjvOJcYI
It's just if you control for air you also just happen to do a lot of controlling for vapour. There's can be a lot of moisture in air, i.e., humidity.
Further there can be some subtleties with moisture/vapour: in many case you want to stop any flow either in or out of the building; in other cases you want to control air but let moisture out:
* https://www.youtube.com/watch?v=zhkGcklWB_Q
* https://www.buildingscience.com/documents/building-science-i...
* https://www.buildingscience.com/documents/insights/bsi-077-c...
Clearly you are using some words differently than I do, but it is not clear to me which ones.
>...blocking rain is just a nice bonus to its primary function.
In our house and our neighbor's houses, blocking rainwater is its primary function - we do not live in a desert.
> Or if you have shingles on your roof that leak (or get blown off in a storm), they can still block UV, but there will be dripping. And that's why you want the control layer(s) further in.
And that is when you need to fix your roof, regardless of what is underneath.
In your replies here, you seem to be trying to turn this into a discussion about water vapor, but I have made it very clear that a) my questions are about what the author has to say about rain and water, and b) the author himself makes a distinction between water and vapor control.
Tellingly, you have nothing to say about this quote from the article:
"Figure 2: "The Perfect Roof"—The perfect roof is sometime referred to as an “inverted roof” since the rainwater control layer is under the insulation and ballast." [my emphasis.]
Wherever you live the sun shines, and UV damage can be extensive against materials that are not designed against it. Cladding is about physical protection to the layers underneath.
> And that is when you need to fix your roof, regardless of what is underneath.
Yes, when you notice it. The shingles may be leaking into the roof structure without you seeing it for a while. Then once the roof has disintegrated, the leakage may go into the attic, which most people don't visit/inspect very often.
So by the time it gets to the ceiling in the livable space, where it is actually noticeable, there could be a lot of damage done.
> "Figure 2: "The Perfect Roof"—The perfect roof is sometime referred to as an “inverted roof” since the rainwater control layer is under the insulation and ballast." [my emphasis.]
You can call the things Foo, Bar, Baz, or whatever you want. The important points are the principals in the design and the order in which the different layers are (ideally) put together.
If you want to argue Joe Lstiburek, be my guest:
>> In our house and our neighbor's houses, blocking rainwater is its primary function - we do not live in a desert.
> Wherever you live the sun shines, and UV damage can be extensive against materials that are not designed against it. Cladding is about physical protection to the layers underneath.
This is a non-sequitur on at least two levels. Firstly, regardless of the truth of your statement about UV, it does nothing to address the point I was making here. If our houses were stripped of their cladding, they would soon fail - from rainwater damage, long before UV took its toll. Secondly, it is yet another attempt to avoid the overall issue, which is the author's position on the placement of the rain (not vapor or UV) barrier.
You seem to think that you can make an argument by quoting out of context and then stating some vaguely related fact, but, unless that fact has relevance, it does not work. Your comment about roof repair is of the same type.
> You can call the things Foo, Bar, Baz, or whatever you want.
This is just ridiculous. You are not even trying to address the question.
> If you want to argue Joe Lstiburek, be my guest:
I am not arguing with Joe Lstiburek, I asked a question about something he wrote, and have ended up arguing with you about what you mistakenly think would work as answers to that question. Your replies make it clear that you are no Joe Lstiburek.
the exterior wall features brick/stone cladding as a primary rain/UV barrier and thermal buffer, and a channel to wick away air, heat, and moisture on its interior, before hitting the "control layer".
the interior wall can be concrete block, steel frame, or wood frame, with only the latter insulated, and with a semi-permeable interior skin (gypsum board + latex paint).
both walls are designed to wick moisture away from the control layer to reduce mold and other problems.
the big downside to these perfect walls are that they're actually two walls, and as such, (roughly) twice the cost of regular stick-built walls, and they're twice as thick, which, given a fixed lot size, reduces interior square footage.
I keep hearing (to my naive/inexperienced/non-builder mind) contradictory advice about how insulated houses should be, and I've been trying to figure out how to square decreasing heating/cooling costs with keeping a house from feeling stuffy.
I guess for stuff like the triple glazing that's not really affecting air exchange in the first place, it's just preventing energy loss, since you're already not doing air exchange through your wall. And maybe getting better insulation in walls means you can crack open a window without it being as much of a problem?
Found this while searching: https://www.ag.ndsu.edu/publications/energy/air-to-air-heat-...
I don't have empirical evidence, however I am pretty sure that we have reasonable air exchange. My evidence for this is threefold:
1) when we have used the log fire, it didn't kill us, or pull the door open.
2) there is still a slight draft,
3) we have a missing floorboard in the understairs cupboard
Whilst all of the air bricks in the rooms were covered, the suspended floor still has four bricks exposed. The triple glazing is sealed UPVC, however in the loft conversion we were forced to have trickle vents (I think thats overkill)
It doesn't ever feel stuffy, which is good. I do need to get a real CO2 monitor though.
One last bit of evidence is how quickly particulates from cooking disappear
Our old house, built in the 1920s had been basically sealed. Since it was only 1600 sqft and had no air ducts, the rooms were small and got terribly icky. Id crack the window open in the winter to get rid of the humidity (in PA, so hardly mild winter).
You have to realize that a lot of moisture from those those 8 tall glasses of water you’re supposed to drink leave your body as vapor. I think I’ve read half the water you expel is through your lungs [citation needed]?
If your house is sealed this water has no where to go. If there’s four of you it gets bad very quickly. This moisture eventually will escape through your drywall, into your insulation and finally through the cracks of tour siding; but that means materials that should be kept dry aren’t
Our new house is very drafty and I dont plan to fix that until I instal a heat exchanger. The air in the new house is much better, and despite being at least double in size our bills have only doubled (ie the added draftiness doesn’t seem to have had that big an effect)
The solution is a heat exchanger. This is a device that exhaust stale air and replacing it with fresh air while passing through a heat exchanger. You can have very large air flows with the outside almost free energetically.
this period is important. otherwise number doesn't mean much to me.
Thats the amount planet's biosphere can process divided by number of peoplle.
To put that stat in perspective, the average carbon emmisions per person [0]:
Qatar is almost 40 tonnes pp
United States, Canada, Australia is about 15 tonnes pp
Switzerland, France, Italy, under 5 tonnes pp
South Sudan is about 0.13 tonnes.
It really puts in perspective how much wasteful carbon reduction and lifestyle changes are needed for us to have any reasonable expectation at curbing this.
Edit: added source
[0] https://ourworldindata.org/grapher/co-emissions-per-capita
The roads are a big part of that in the US. American suburban car dependency needs to die.
All construction activities including roads, account for about 10.6% of emissions.
For comparison energy use inside buildings accounts for 17.5% of emissions. Transport emissions (Land, Air, water) account for 16.2%.
There are absolutely lifestyle choices at play here: Size of houses, size of car engines, car tonnage, commute distances, Travelling/Shopping habits.
We cannot change minds and infrastructure overnight, the second best thing we can do at a policy level is to (magically) find ways for our energy production to not depend on coal/natural gas.
The more spread out people are, the further water, electricity, gas, sewage, trash, food, human bodies, and everything else has to travel. Energy is mass times acceleration times distance.
In other words, detached single family homes with garages and 2 cars driveways on a quarter acre lot preclude any environmentally conscious changes one could make, barring the miraculous discovery of some new technology that supplants fossil fuels. Or drastic reductions in population.
The simple, but not politically viable, solution is to increase fossil fuel taxes so much that it forces people to give up detached single family homes and individual cars and move into apartment or rowhouses so that public transit can be implemented.
Do you have a source for this claim?
All I have read until now points to a majority of individual emissions associated with vehicle emissions and Energy usage for Heating/Cooling houses/offices. I am all for a vegetarian lifestyle for animal welfare sake but I feel this focus on Agricultural emissions is misleading or at least misreported.
If you move a load of produce in a truck, do the truck emmissions get counted as "transport" or "agriculture"? I guess depending on your angle, you could say either.
The paper you link includes CO2 'equivalent' emissions, i.e. they are including NOx from diesel engines and Methane from oil/gas extraction and calculating some CO2 equivalent volume. Whereas the source I referenced is only including CO2 emissions.
i.e it's not that common French is more carbon economical than a Canadian - she just happen to have been born in a place with established nuclear power generation.
In other words - this stat means nothing.
https://ourworldindata.org/grapher/co-emissions-per-capita?t...
The trend is almost binomial, many of these countries have marginal nuclear use.
But with cold bridges and such it can be a little complicated to get right.
But for things like heating, latitude makes a big difference. I did some calculations for a fanfic I wrote, and at a moderate 30°N or so, you basically get the same insolation as Rovaniemi in Finland assuming similar atmospheres. No wonder those characters never got sunburns.
Not sure about that. Plants absolutely love insolation!
It drives me up the wall, winters are not long and it doesn't get that cold but there's a few days a year when the weather drops to around 12 degrees celcius within my apartment (so 54 degrees Fahrenheit) and as someone from colder climes that's used to central heating, I'll say that I much prefer a cold winter with a warm home than a mild winter with a super cold home. I've seen the same when I lived in Japan...
Additionally due to the poor insulation, you get to hear the noise outside quite a bit which I personally hate.
However, there is still a significant amount of single-glazed properties in poorer areas or in listed historical buildings.
I think that might change as we go towards energy efficiency, we need to swing the needle back towards more efficiency = good.
It would have been nice to add a calculation of the energy required and CO2 produced to manufacture, transport and install that roof.
I feel this is an important metric that is generally ignored in these conversations. And yet, it is crucially important in order to determine the true outcome.
That said, I understand just how complex this input can be to obtain. You can’t reduce it to a number per window. That’s not how it works.
In order for someone to produce those ten (or whatever) windows somewhere in the order of twenty companies must exist and operate constantly. Aluminum mining and processing, steel production, extruders, paint/coatings, chemicals, oil/petroleum, fasteners, cardboard and foam packaging, forklifts, trucks, CNC machines, computers, etc.
The point is: These companies don’t exist just for the 42.5 minutes it took to assemble and pack the windows. In order to be able to buy ten windows, they have to exist whether or not someone is buying that model window or not. The energy required and CO2 produced comes from the combination of all of these factors. And, yes, this is hard to estimate. Yet the numbers are very far from zero.
It’s like saying you are going to go live in a tent on a small island to reduce CO2 emissions while ignoring the car ride, flight and ferry that get you there and the freighter that delivered your possessions.
I'd also like to point out that with switching from gas to heat pump heating/cooling you'd probably save even more on your bills and have 0 on-site carbon emissions and likely 0 off-site emissions as your electricity starts coming from non-carbon sources. Heat pumps are around 3x more efficient than the most efficient gas heating because they're just moving heat around, not creating heat.
As Saul Griffith says[0], "You can't 'efficiency' your way to 0" (meaning 0 emissions, which is what we need).
Efficiency is a great win for our bills and cutting some emissions but even if every building made their current systems more efficient, we'd still be on track for over 1.5C of warming. What we need is transformation, and most of that to electric heating/cooling/transport/cooking. And we need it fast, all across the residential and commercial economies in the next 2 decades with more in the next decade. It's going to be a war-time-like effort. Thanks for getting it started!
Now I'm wondering how the comfort varies with the temperature of the walls (due to infrared radiation), which are obviously much colder in the winter than in the summer.
Needless to say that thermal insulation is awful in IT.
https://lawline.se/answers/hur-kallt-far-det-vara-i-hyreslag...
Personally I find if it's especially cold outside, I need to put the thermostat up to compensate.
However that doesn't dictate inside temperature. Well, maybe if you heat with firewood - you will get high/low temperature rises/drops. But people just like 20+ inside. 22-23C for me is comfort. Currently 24C at office - higher is out of comfort, but happens.
Someone like lower temperatures. Someone wants to save some money and keeps temperature lower than comfort.
And yeah, warmer climate results in colder inside temperature, because houses are not very well insulated and may not have advanced heating systems. But that's just experience from few data points I know of (and some HN comments confirms that).
When it’s -25C out, not so much.
Japan can actually be a case study of that: detached homes on Honshu (the main island) generally have poor insulation, in winter they tend to be quite cold and spot-heated (using kotatsu and kerosene space heaters, with heavy clothing).
On Hokkaido meanwhile, good insulation (including double or triple pane windows) and central heating are common (the island has insulation regs and there are loans dedicated to properly protecting against the cold), and inside temperatures tend to be cosy. It’s a regular occurrence that Hokkaido residents catch colds when visiting tokyo in winter, because they don’t have the habit of bundling up inside.
Though when it comes to Honshu, one of the justifications for the lack of insulation is the difficulty of keeping indoors drafty and dry during the extremely wet summer, to avoid the walls outright rotting on you.
I think that its all about the windows. In warm climate regions they are made to allow air circulation.
Windows, walls, roofs, ceiling heights, …
In warm climates until you have AC you want shade and air circulation / drafts.
Having no roof insulation is not much of an issue (might even be advantageous to trigger forced airflow) as long as you’re far from the roof. Likewise high ceilings keep the heat climbing above head level.
And imperfectly adjusted doors and windows with dodgy (or missing) seals isn’t a bother when it’s not an advantage.
In cold climes none of those is really acceptable unless you want to absolutely nuke your bank account on heating, at least if the house is anything more than a place to sleep in.
It's the other way around. Indoor temperature varying with the outdoor temperature is one of those weird things you experience when going abroad from your colder climate, at least in Europe.
I don’t know if I live in a cold climate but people will start to complain if the temperature goes below 21C indoors.
Personally in winter I heat my house to 14c as a minimum, 20c in the living room and office. Reason being I only need warmth if I'm sat down and not moving, so any higher and I start to get too hot.
My temperature is now approaching absolute zero.
So I wear 3-4 layers, including fingerless gloves and a hat. It looks ridiculous, but nobody sees me. And in summer, well... I don't wear much or anything. I at least put on a shirt for video calls :P.
Frankly, it sucks; and this is my last year here before I go nomad full-time.
Back in 2012 to 2015 I worked most of the time I think in the radio lab at the company I worked for at the time. Temperature was often above 30 degrees in the summer. I didn't think much of it back then, went into office, started working and forgot everything but after a while I realized I was drinking 1.5l water during the work day without needing to visit the restroom and I would be exhausted when I came home.
It was noisy and warm but almost no interruptions and still very nice compared to insulating an attic in in the summer (I've done that too so I know.)
(This winter I tried working from the garage in December but at below 0C it gets impractical even with really warm clothing.)
These conditions are improper for extended work hours and intellectual work. I don't know how it is on your country but generally there are regulations regarding that. For offices the ideal climate is ~25 degree C, 40-60% humidity and <1m/s wind.
Have my upvote, I agree. But let me share why I sat there if you want (warning, somewhat violent towards the end):
I wasn't supposed to be there but the alternative was working in an open floor plan office where everyone from project engineers to service managers had access, and that was purpose-built to be cool so that it could be shown to customers.
> I don't know how it is on your country but generally there are regulations regarding that.
Norway is good at this but sadly we don't have effective regulations against managers who come into the room "joking" about impaling some people from another culture on our coat rack :-/
In my case I found it better to stay in the radio lab instead of risking that conversation or another one like that going in the background while I was one the phone with an important customers.
My point was only that I had a really really nice office but preferred the hot and noisy radio lab strongly.
> (assuming a 0.3g of CO2e per kWh
It's kg there, not g.
And this number is for the electricity, gas is 0.203 kg per kWh.
If you are indeed heating with electricity, in france the electricity CO2 is almost always below 100g of CO2e per kWh.
Note: I suggest using underfloor heating, it should be more efficient with a glass roof, because there is less hot air to raise to the top of the house.
Buildings like this in Paris are often so tightly packed together that windows in walls barely provide any light. Replacing the roof with a more standard one would necessitate giving up any daylight and having lights on all the time.
Unless you're losing heat through the floor I doubt that temperature difference between the floor and ceiling is accurate with a radiator system, perhaps if you measure it 30 minutes after you turn on the heat, but throughout the day the temperature should be mostly consistent throughout the room unless you're losing heat through the floor.
The underfloor heating uses a low temperature; the floor is ~24 C. There is little air movement because there is a very small temp gradient. With a radiator or a stove, its temperature is much higher, prob > 60 C. So you will have a column of hot air that rises to the top of the room and stays there. And at the floor level it is much colder.