The following are facts that have broad application in other climates as well as Hot and Humid.
Someday, Demand Control Ventilation DCV will likely be used in all occupied buildings including homes, schools, libraries, workplaces, churches, auditoriums. The Florida Power FPL web “encourages” the use of DCV for reason of significant reductions in use of electricity for heating and cooling. Energy savings of 20% to 60% are frequently achievable. It is easy to see why power companies have a second and concealed agenda in opposition to DCV. Some scientists advise that switching to DCV will slow the onset of climate change by reducing energy use. . . . As it reduces the dividends to power company stockholders and bonuses to executive officers.
IS MOISTURE A SERIOUS ISSUE? You can expect that in south Florida, on an annual average, each cubic foot of outdoor air that you add to a building adds 1.62 pounds of water vapor (water) in 24 hours. So if you add 100 cubic feet per minute of outdoor air 24 hours a day, your additional moisture load (from ventilation) is an annual average of 162.5 pounds of water each day. The equivalent of allowing a sprinkler to spray 20.31 gallons of water into the home each day. Quite an additional load for an air conditioner to dehumidify and quite a lot for a even a large capacity dehumidifier to remove.
- SO WHAT HAPPENS TO THE MOISTURE THAT THE AIR CONDITIONER CANNOT REMOVE? Simple. It soaks into everything, all furnishing and personal property and building materials which will act like dehumidifiers pulling moisture out of the air until moisture saturation reaches about 70% by weight and mold will suddenly start to grow everywhere on on nearly everything.
So what can be done to prevent that?
- Seal all “Radon Fountains” and other floor slab penetrations.
- Remove the sources of all indoor air contaminants to reduce the quantity of outdoor air required to dilute contaminants
- Don’t ventilate unless the breathing zone is occupied.
- Ventilate only at a rate necessary for the number of occupants present and according to the contaminant load.
- If no one is present, stop ventilating
How can we make that happen?
- We can use carbon dioxide controllers, passive infrared sensors, door open triggers, radar, sound sensors, light interruption beams.
- However, carbon dioxide is the only means that can keep accurate track of the number of occupants as they come and go and their activity level. Based upon that, the CO2 controller can direct the ventilation system to adjust its speed accordingly to ensure that sufficient ventilation is provided and over ventilation never occurs..
- Demand Control Ventilation is accepted by ASHRAE. DCV supplies ventilation air at variable rates according to the number of occupants so that each occupant has acceptable fresh air delivery. Carbon dioxide created during each individual’s breathing can be measured, and the number of occupants and their activity level may be determined by a CO2 controller. The controller then directs the ventilation system to change speed as necessary to accurately serve the number of occupants present.
- During vacancy, no CO2 is added from occupant respiration so no ventilation is required. No water vapor is added.
- Demand control ventilation varies the ventilation rate to achieve a constant 1100 parts per million CO2 which correlates to 15 cubic feet per minute per occupant.
- But recent research has revealed that cognitive function and sleep are remarkably improved when CO2 levels are maintained at around 600 parts per million.
so why would homeowners/buyers be attracted to ventilation and why would they pay a premium for it?
The described ventilation system would provide the following:
- Near total elimination of entry of wildfire smoke into a home’s breathing zone.
- Reduced exposure to outdoor allergy and asthma triggers. Pollen season would mean nothing if they stayed indoors.
- Reduced exposure to VOCs, acrolein, PM2.5, agricultural chemical aerosols, carbon dioxide, household odors, outdoor soot, smoke, radon
- Increased indoor oxygen levels
- Risk of mold and moldy odors decimated