A challenge to heat and cool buildings efficiently

The efficiency with which we can heat and cool rooms requires a good solution for maintaining low carbon dioxide levels in well-insulated rooms.

Exchanging large volumes of air from inside to outside when the outside air temperature is very cold or hot could be a very costly way to remove small amounts of carbon dioxide.

 

An adult uses about 500 litres of oxygen while breathing about 10,000 litres of air in and out per day.  

See "Oxygen a person uses each day."

A carbon dioxide concentration of 1,400 ppm reduces decision-making ability by 25%. 

See "Rising carbon dioxide ...may directly harm our ability to think."

How much does the CO₂ concentration increase in one day, depending on the total volume of air in a sealed room, with one person occupying it? 

A room that is 4 metres long by 4 metres wide and 2.5 metres high has a volume of 40 cubic metres. 

It contains 40,000 litres of air of which about 32,000 litres (80 percent) are nitrogen and about 8,000 litres (20 percent) are oxygen. 

One person will use about 500 litres of oxygen in a day. So the 8,000 litres of oxygen in this room is ample for one day. However, the small amount of carbon dioxide the person exhales raises the concentration of carbon dioxide so that quite soon it will interfere with the person's ability to think clearly if it is not removed.

One person sleeping or working in this room alone for 8 hours would raise the carbon dioxide concentration to over 4,000 ppm if there was no exchange of air from outside, and no method to remove the carbon dioxide being added. 

The relatively small amount of carbon dioxide - increasing by 21 litres per hour - requires a large volume of air in the room - 40,000 litres - to be either exchanged or otherwise processed each hour to maintain the carbon dioxide concentration at a constant level.

Classrooms with high carbon dioxide levels may be lowering education outcomes for children because their ability to concentrate is being reduced.

Hour	Air Breathed (L)	N2 (L)	O2 in (L)	O2 out (L)	CO2 out (L)	CO2 conc (ppm)
0	-	-	-	-	-	-
1	417	333	83	63	21	521
2	833	667	167	125	42	1,042
3	1,250	1,000	250	188	63	1,563
4	1,667	1,333	333	250	83	2,083
5	2,083	1,667	417	313	104	2,604
6	2,500	2,000	500	375	125	3,125
7	2,917	2,333	583	438	146	3,646
8	3,333	2,667	667	500	167	4,167
9	3,750	3,000	750	563	188	4,688
10	4,167	3,333	833	625	208	5,208
11	4,583	3,667	917	688	229	5,729
12	5,000	4,000	1,000	750	250	6,250
13	5,417	4,333	1,083	813	271	6,771
14	5,833	4,667	1,167	875	292	7,292
15	6,250	5,000	1,250	938	313	7,813
16	6,667	5,333	1,333	1,000	333	8,333
17	7,083	5,667	1,417	1,063	354	8,854
18	7,500	6,000	1,500	1,125	375	9,375
19	7,917	6,333	1,583	1,188	396	9,896
20	8,333	6,667	1,667	1,250	417	10,417
21	8,750	7,000	1,750	1,313	438	10,938
22	9,167	7,333	1,833	1,375	458	11,458
23	9,583	7,667	1,917	1,438	479	11,979
24	10,000	8,000	2,000	1,500	500	12,500

You can add mechanical ventilation to your home with a heat recovery ventilator (HRV) or energy recovery ventilator (ERV). Both exhaust air from the house and bring in outdoor air to replace it. There's a heat exchanger to bring the incoming air to a better temperature.

5/11 pic.twitter.com/geOQQnTecQ

— Joey Fox, P. Eng, M.A.Sc (@joeyfox85) July 20, 2022

Below are extracts from two articles - the first on symptoms in people in rooms with elevated levels of carbon dioxide, the second on symptoms of people in hotel quarantine. 

The similarities may indicate that people in hotel quarantine were being affected by elevated carbon dioxide levels, and not the fact that they were in quarantine. This could be evaluated by comparing the group in hotel quarantine with the experiences of those in quarantine at Howard Springs with self-contained units and access to fresh air.

Rising carbon dioxide ... may directly harm our ability to think

Extract from article published in ScienceDaily:

"It's amazing how high CO2 levels get in enclosed spaces," said Kris Karnauskas, CIRES Fellow, associate professor at CU Boulder and lead author of the new study published today in the AGU journal GeoHealth. "It affects everybody -- from little kids packed into classrooms to scientists, business people and decision makers to regular folks in their houses and apartments."

Shelly Miller, professor in CU Boulder's school of engineering and coauthor adds that "building ventilation typically modulates CO2 levels in buildings, but there are situations when there are too many people and not enough fresh air to dilute the CO2." CO2 can also build up in poorly ventilated spaces over longer periods of time, such as overnight while sleeping in bedrooms, she said.

Put simply, when we breathe air with high CO2 levels, the CO2 levels in our blood rise, reducing the amount of oxygen that reaches our brains. Studies show that this can increase sleepiness and anxiety, and impair cognitive function.

They found that ... indoor concentrations ... of 1400 ppm to be harmful.

"At this level, some studies have demonstrated compelling evidence for significant cognitive impairment," said Anna Schapiro, assistant professor of psychology at the University of Pennsylvania and a coauthor on the study. "Though the literature contains some conflicting findings and much more research is needed, it appears that high level cognitive domains like decision-making and planning are especially susceptible to increasing CO2 concentrations."

In fact, at 1400 ppm, CO2 concentrations may cut our basic decision-making ability by 25 percent, and complex strategic thinking by around 50 percent, the authors found.

Hotel Quarantine And Mental Health

Extract from article by Giulia Fiore, psychologist and founder of Confidence to Achieve:

Hotel quarantine is a costly procedure that necessitates a highly specialised workforce to sustain the system, which includes clinical, welfare, and security services, in order to minimise risk and meet the duty of care obligations. The effects of hotel quarantine on mental health and wellness are arguably one of the most important factors in the hotel quarantine scheme, as even those who have never encountered mental illness may find the experience taxing.

Isolation and quarantine have been shown to have negative mental health effects, including depression, anxiety, stress-related disorders, anxiety and anger. In a rapid study, Brooks et al. found that people who were quarantined have more negative psychological effects, such as post-traumatic stress symptoms, confusion, and frustration. Furthermore, citizens in a state of confinement can experience restraint and express fixation on the disease’s progress, as well as psychosomatic symptoms such as insomnia.