Water is dripping from one ceiling vent in our air conditioning system which was installed this spring. I assume that the water is condensation since the problem started as the weather started to cool. Right now it’s only the one vent and only a sprinkle but winter has not yet started.
The heating system is electric baseboard so a/c system was installed entirely in the attic. Following regular Canadian building practice the attic is well ventilated with outside air, now getting to -5C (22F) at night. Installer wrapped all plenum with fiberglass insulation – but did not wrap the air handler unit (not sure why not or whether this is a/the problem). There are 8, 6″ vents in all, a supply and return in each of 3 bedrooms and hall.
The dripping vent is in the master bedroom and is also the furthest from the air handler – about a 30′ run. All 8 vents are equipped with a damper all of which have been closed for a month or more.
I assume that the problem is caused by moist air from the house escaping past the dampers, which do not seal perfectly, then condensing in the cold pipe leading to the vent. Does this make sense?
BTW, we have ceiling fans in the bathrooms connected to a common fan via insulated (flexible) 5″ pipe and had no problems with them in 8 years.
Before I contact the installer I’d be interested in opinions about what they should have been done to avoid this problem which I assume would potentially be common to all attic systems.
Replies
How about air-sealing the attic with a spray-foam insulation, thereby making the attic "conditioned" space along with the rest of the house?
TF
After reading another Breaktime thread on spray-foam I see what you mean, but don't know if it is feasible. I can see from this other thread there are pros and cons.I currently have 6" of insulation between the attic and bedrooms below. Current recomendation for this part of Canada (3500 to 5000 degree-days) call for R32, about double what I have. I have been thinking about beefing it up with batting laid perpenduclar to the joists. If I went the spray foam route, I don't know what the R factor for spray foam is, but it sounds as though it would need to be nearly a foot thick. If I am following you this would be on the underside of the roof deck and gable ends. I wonder as well about fact that the roof trusses and decking would no longer be ventilated, something that seems to be regarded here as very important to prevent mosture damage to the roof structure.
You need more insulation to keep the duct pipe at the house temp and not the attic temp. The little bit of insulation wrapped around the ducts is only about R 6, where you are you should be looking at R 38 over all the duct work.
Should the Air Handler (about 30" x 18" x 18") be insulated too? The installers did not put any insulation around this. To your point, the flexible pipes (looks like factory insulated) onneting bathroom vents are overall about 12" diameter which means they have about 3" of insulation
For the nonce, at least, tape plastic over the vent openings.
Yes, I think this is a good idea, and its easy to try. If this fixes the problem then is there a "proper" solution? Family is not too keen on the look of plastic taped over the vents! I think the installer should have anticipated this problem which is not brought about by some unique characteristic of my house but rather characteristic of the local climate. It is true that it would be more common to add a/c to existing forced air heating system.I wonder if they should have used vents with a damper having a better seal. Is such a thing available?What I am really bothered about is what happens come spring if the problem goes unchecked. Just now we are seeing a sprikling of water. It is not unusual in January & February to have 8 weeks when the outside temp does not go above freezing. If through this period condensation freezes and ice builds up in the a/c piping in the attic then we may have more of a waterfall on the first nice day of spring.
Another temporary fix is to keep the humidity inside lower. If you have a furnace humidifier, run it at a lower setting than you otherwise would. If you have an air-air exchanger, run it more frequently to exhaust more moisture.To me, any attic HVAC system in northern climates just doesn't make sense, unless the attic is insulated or the HVAC system is very carefully sealed and insulated. My first take at a permanent fix would be to somehow box in the entire HVAC system to bring it into the house "envelope", but a lot depends on the specifics of the situation.
Seven blunders of the world that lead to violence: wealth without work, pleasure without conscience, knowledge without character, commerce without morality, science without humanity, worship without sacrifice, politics without principle. --Mahatma Gandhi
Hmmm! Thanks for the comment and I take your point "any attic HVAC system in northern climates just doesn't make sense". Boxing in and insulating the air handler and main plenum may be feasible, but this would leave maybe 140’ of 6" duct to and from the 8 ceiling registers which run through a very complicated attic. If may be of interest so I will explain why we have this system.We chose this installer and attic based system after talking to a number of local HVAC contractors. Each contractor had alternative ideas but we chose this contractor because their proposal was least disruptive to install, least unattractive inside, and also non-Freon (Freon systems can still be sold here I think to 2010).What makes the situation relatively unusual is that the original house was built in 1832, a log (10"x14") one & half storey homestead typical of many in the area built at the time. In 1968 the previous owners did a major renovation including new foundation for log home and “extensions” so that now the log home is about 40% of the living space. Many inside walls are either exposed original logs clear pine plank panel or, in the log home, lathe/plaster. All ceilings are drywall and insulation is better than would have been regulation in ’68. The outside is white stucco; we are in the country near lots of trees and in Ottawa Canada. As consequence of these factors (I think) we have never found the house to be excessively hot. After discussing options with prospective contractors we decided that air conditioning the 2nd floor only (about 38% of living space) would significantly improve summer comfort. They said (we didn’t check) they have installed similar systems in the Glebe, a local area with many century plus older homes. Based on experience in July the system works well. Part of the rationale for this attic system was that if it was not adequate additional capacity could be added to the ground floor which has easy full basement access. At some point in time we may replace electric baseboard heating with something else (e.g. forced air propane/gas/oil). The family is not keen on this since they would loose the ability to control the temperature of each room individually. From an environmental perspective and, increasingly, operating cost perspective electricity does not look so bad.
OK, it wasn't that clear that this is a retrofit, especially to such an old structure.Oddly, a solution to your problem (at some cost in additional heat loss) might be to run the AC fan on low speed through the heating season, at least when temps are sufficient to cause this condensation problem. This will keep the ducts and AC heat exchanger warm and prevent condensation. Then you can pile on insulation wherever possible to minimize the heat loss, but you won't need to achieve 100% coverage.
Seven blunders of the world that lead to violence: wealth without work, pleasure without conscience, knowledge without character, commerce without morality, science without humanity, worship without sacrifice, politics without principle. --Mahatma Gandhi
Good idea Dan, thanks again.