That would be nice

Robert O'Brien

https://www.forbes.com/sites/forbesrealestatecouncil/2020/05/14/how-a-pandemic-could-transform-todays-home-into-tomorrows-sanctuary/#2bc1a5529c5f

"Traditional forced air systems may increase the risk of household infection by spreading viral particles in recycled air and allowing those particles to live longer by decreasing humidity. Alternative heating systems like radiant heat may become more prevalent. Well-insulated homes that stay cooler in summer and warmer in winter will become an even greater priority."

Steamhead

I've seen that point made in quite a few Dead Men's Books. Everything old is new again.

motoguy128

Low humidity preserves viruses? I thought they needed moisture to survive. I believe most data shows that virus infection from surface contamination is rare. Airborne droplets from someone talking, coughing or sneezing is the primary transport mode.

Furnaces drying out a home is a myth. They don’t remove moisture.

Radiant heat is great, but you still need Air Conditioning in summer. So radiant heat doubles the cost of the installed system.

For service techs that work in areas with a wide range of social demographics... there’s a LOT more low hanging fruit out there for healthy home environments.

The Steam Whisperer

"Furnaces drying out a home is a myth. They don’t remove moisture."

They may not directly remove moisture, but they do create massive air leakage in a typical home ( There's all sorts of DO
E testing out there to back this up) , which brings in cold outdoor air. This air, when heated to 70F, has a relative humidity of about 15%.
Like most myths, there is a truth behind them.

I agree that there is a lot of other low hanging fruit our there, but getting rid of forced air heating and cooling systems ( like the rest of the world) would dramatically improve the health conditions in our homes in the U.S. and cut our energy usage.

Jamie Hall

As @The Steam Whisperer (Formerly Boilerpro) says, heating a house -- by whatever means -- does not, directly, reduce humidity. What does reduce humidity is heating cold outside air for whatever reason.

Therefore...

If you are concerned about low relative humidity in the winter time, reduce the air infiltration (which, for those with air conditioning, will also reduce the high humidity in the summer time, by the way). On the other hand, if you reduce the air infiltration enough -- below two to four air changes per hour, depending on whom you read -- you get a host of other indoor air quality problems.

If the structure is much tighter than two air changes per hour, you really should have a sensible heat heat recovery ventilator (NOT, emphatically, latent heat heat recovery!) to keep the heating load (or cooling load) down to what you thought you were paying for when you tightened the building up that much, while at the same time keeping the indoor air quality at least no worse than the outdoor air quality.

As to low hanging fruit -- oh my word yes. But proponents (or opponents) of one specific way of heating a building versus another confuse the issue tremendously, and needlessly. There is no good excuse for any fuel fired heating system to have an energy conversion efficiency of at least 80% all the time, given proper maintenance and, especially, installation. Some newer fuel fired systems can, at least in the shoulder seasons, go higher -- as much as 96% for some. The fuel conversion efficiency within that range is not a function of the type of heating system; those which can run at low return temperatures (whether the moving fluid is air or water doesn't matter) can run at the higher end of the range when they can run at low return temperatures -- and the boiler or furnace is designed for it, and the system is designed and installed to take advantage of that capability.

Heat pump systems -- when they can run with a COP higher than about 3 -- are more efficient than a local fuel fired unit, in terms of overall energy efficiency (taking into account electrical generation and transmission efficiencies), unless the electricity is being generated by non-fuel fired renewables or nuclear power; there are, of course, other environmental costs associated, however.

Passive or mildly semi-active solar can, in most of North America, achieve zero outside energy usage except for a small amount of fan power (for semi-active and the heat recover ventilaor). It is not a suitable system for retrofit, however.

Bottom line -- the low hanging fruit, and there is a tremendous amount of it -- is in proper maintenance and, where necessary, correcting installation or control errors, and in tightening building envelopes up to a point.

JUGHNE

I believe that old school gas furnaces with standing pilots and perhaps 6" flue pipes pulled in enough air during combustion that the cold air would dry out the house.
In the 60-70's houses with gas furnaces usually got a humidifier,
where as electric furnaces/heat pumps houses almost needed a dehumidifier.....no chimney action.

ethicalpaul

Does my steam boiler pull in about the same air due to replacing what goes up the flue as a forced air furnace does? Honest question.

Jamie Hall

Yes -- so far as replacing what goes up the flue is concerned.

JUGHNE

Air out would match air in in any case.

But a CI boiler without the vent damper could, IMO, pass more air up a chimney than an old school FAF.
The mass of the cast iron and water being hot almost constantly would induce gravity flow up the chimney thru the burner compartment and boiler flue exhaust passages, cooling down that heat sink of CI and water.

Newer furnaces have an inducer exhaust fan with perhaps a 3" discharge.....probably minimal gravity flow upward there.
Then the 90+ FAF's have the ability to pipe in combustion air so no indoor air would be lost. I have seen some 80+% with that feature also.

mattmia2

JUGHNE said:

I believe that old school gas furnaces with standing pilots and perhaps 6" flue pipes pulled in enough air during combustion that the cold air would dry out the house.
In the 60-70's houses with gas furnaces usually got a humidifier,
where as electric furnaces/heat pumps houses almost needed a dehumidifier.....no chimney action.

In a well designed and installed system where the airflows are balanced, that is probably the case. Where joist and wall cavities are panned for air returns and little thought is given to design or balancing as is the case in most quick and cheap mass produced housing, the blower creates rooms with higher and lower pressures compared to the outside which increases infiltration and exfiltration in those rooms.

The Steam Whisperer

From the gist of what I have read of The DOE testing, it was the presence of the ductwork ( about a 10% increase in air leakage) and the blower fan ( IIRC about a 70% increase in air leakage) that increased the air leakage of the structure.