Is heating system to blame for mold?

MoldyGuy

The heating system in our rental is single pipe steam heat. Whenever the system runs, we hear the hissing and sometimes see steam coming out of the radiators. First night...it woke us up, but we got used to it. Each radiator has a dial/valve thing you can adjust although some of them do not adjust anymore and are stuck in position.



We have mold growing on every windowsill and condensation on all exterior walls that cause mold to grow. Every window in the house is half covered in condensation and water pools on the baseboard in some places.



The relative humidity in the house ranges from 50-60% most of the time. This is an older house/duplex probaby built in 1920 or so. I doubt the system has been serviced recently.



The landlord had a cleaning crew come and remove the mold--apparantly something they have had to do repeatedly for other tenants in years past. Most windows are replacement vinal windows, but they are still covered in water. I don't know if the walls are insulalted or not.



I'm thinking the heating system is to blame here. I'm hearing it in stereo right now as it hisses constantly while it is on, but I don't know if that is normal or not.



additional data point: after scraping dust off system, I discovered a tag--installed in 1985. No evidence of service tags or indication the system has been "disturbed" since...

Jamie Hall

Relative humidity

If your relative humidity is really 50 to 60 percent, it is unlikely that the heating system is to blame.  Rather, it is cold walls and windows.  I have seen this with forced air heat, as well as steam and hot water.  All you need is a nice cold surface.  You probably have minimal insulation -- if any -- and I wouldn't be surprised to see pretty high infiltration rates, new windows or no.  All of which will give you the nice cold -- and wet -- surfaces you are finding.



I would note that air much dryer than that is very uncomfortable for the people in the space; ideally the RH should, in fact, be higher.



That said, however, the vents really shouldn't hiss and leak steam.  The chances are that the steam pressure is set too high -- that's rather common -- and may have damaged the vents.

MoldyGuy

thanks

thanks for the info. Yes, the system is very inefficent. Our first gas bill showed 4 therms/day usage in October...this is for an 800 sf space. This is in New England...it's about 15 degrees outside right now.

Jamie Hall

You say this is a rental?

Do you have a decent relationship with your landlord, and can you persuade him that with your help and a little help from the Wall we may be able to make things work a lot better, and cheaper?  Because we would be happy to help!



I live in New England, too -- and am the building super for a 7,000 square foot museum.  And it is 15... and old faithful in the basement is having a field day, but it's not inefficient!



The cold surface condensation problem, by the way, is a real bear to do something about while keeping the RH in something resembling a comfortable range. 

Kevin_in_Denver_2

Indoor RH

Jamie,



50-60% RH indoors in the winter with 15F outside is a total recipe for mold.  The window manufacturers and the humidifier manufacturers recommend more like 35% because of  "sweating problems"



So yeah, there is too much steam leaking into the living space.



 But I agree with you that 50% is more comfortable than 35%.

nicholas bonham-carter

excessive humidity

we boil water on the stove to get the humidity up in our very old house, and can never get much condensation on the windows. i would definitely check for leaks in this system, by turning off any auto-fill, and marking the sight-glass to see if there is any waterline drop over a few days.--nbc

Jamie Hall

You're right, of course

with normal indoor temperatures -- my view point gets distorted by the building I care for.  It's a museum (with a live in apartment for me, fortunately!) and the folks who care for the collections let me run it at 60 indoors, which helps a lot.  They tend to get cranky -- particularly the gal who cares for the pianos -- if the RH goes below 50, and I will admit that I have to be on guard against condensation on the windows (not on the inside, on the storm windows) if it is very cold out and not windy.