Hip roof – too much moisture? Wet nails…
Hi,
We live in northern New England where the summers are pretty hot and winters are cold.
House facts/tidbits:
*We have a hip-style, 2 story house. Shingled roof. The peak has a ~4 – 5′ ridge vent. Built in 2005.
*3 bedrooms and 2 bathrooms on the 2nd floor, 1/2 bath with a vent on the 1st floor
*We have two bathroom vents that vent out through the roof (2nd floor bathrooms). Both of those ducts are insulated now (I just finished this weekend).
*I sealed up any holes around the bathroom fans, PVC pipes, etc.
*Our oil boiler vents out via direct vent out on the side that has the most white stuff in the attic.That direct vent is at least 25’ from the soffits.
*We have a gas fireplace in the living room that is not vented, we use it a lot during the winter.
*The house did not have an attic entrance when we moved in 2010. The first winter or two, we had large icicles hanging from the roof edge. I made a small entrance into the attic and found just one layer of insulation. I put another layer in. I later installed an attic door system (frame, ladder, etc) from Home Depot. — EDIT – No for ice dams
*Basement rim joists were spray foamed (it’s the 2 type mixture and am not sure if it’s open or closed cell) the basement rim joists 8 years ago.
*All of the lights, fans, etc, are sealed by either a foam boxed around them or caulked, the attic entry has a foiled faced insulated tent around it.
*Each roof soffit bay has the styrofoam baffles that go down to the perforated soffit and about about 1/2 about the bays~. If I look down the baffles, I can see light. Under the baffles, installation is crammed up against them. I did remove some that looked too tight.
*We have no central ac or HVAC
I went up into the attic to check something and I noticed that on the north and east side of the roof plywood is white fuzzy looking mold. Most of the nails are dripping water. Not all of the bays have this white stuff, some do, some it’s in one area, some it’s 3/4 of the bay up to the ridge and some don’t have it at all.
I’m not sure that I’ve noticed this stuff before. The house is about 16 years old.
I’m going to buy an insulated zippered attic door tent that better seals and just flatten the current tent and place it on top.
I am waiting to hear back from a company that performs audits but I believe that we may not have enough ventilation or insulation. I’m looking for thoughts and advice. Thank you!
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Replies
I never have liked ridge vent. Putts me in the minority. Hip roofs never have enuff ridge to exhaust ventilate. They are mostly hip. You need to ad ventilation in the attic with pillow vents. About 8 would be a guess. Based on your description you have about a 1.000 sq. ft attic.
Better ventilation may be part of the solution, but it'll also help to really figure out where the moisture is coming from. The ice dams suggest air leaks in the attic floor, probably near the wall to roof intersection.
An audit would be helpful in tracking down where air is leaking into the attic from indoors. Figuring out your interior humidity levels may also be worthwhile. I've never understood why unvented gas appliances are considered ok.
You mentioned seeing more 'white stuff' on the side where your oil boiler direct vents. Is that also the north side?
The weather this winter in Maine has been such that you might find dripping nails even under a fully open (well-vented) cold attic just from strange temperature and humidity swings, but you clearly have some mold growth so you've got more moisture input than output over the long-term it seems.
I imagine you may need some combination of improved venting and pin-pointing your moisture inflows. Someone knowledgeable on-site with testing equipment (such as an auditor) will be valuable for this.
Check your soffit vents. I think of a hip roof like an airplane wing if you have good soffit vents. When the wind blows across the roof it has the choice to go over the roof or thru the soffit thru the attic and out the other side. It is a longer path over the roof than thru, so if it is easier to go thru it will unless something is blocking the flow.
Pull down attic ladders are notorious for leaking and poor insulation. This may not help in the long run.
Seal a box fan in a window and use the smoke from incense sticks to find the leak in the ceiling.( shut off gas appliances first)
FYI the nails are rusty because they are wet. The nails get the sheeting wet it rots around the nail the nail gets loose and the shingle blow off the roof.
Walta
I should ave mentioned this in the first post- the ice dams are non-existent now. With my untrained eye, it appears that the soffit vents are OK, I can see light coming up through the soffits through the baffles when the light is off but shouldn't I feel a decent draft or not? While working on the insulation of the bathroom vent, I did feel a light draft but I was right to the baffel.
As for the direct vent, I asked our furnace guy who is very experienced with different venting and he though that due to the height (the pipe is below grade, or at least the ground slopes much lower that the other sides of the house) it shouldn't cause the problem. That is the north side as well.
I did not read carefully and missed that you have an unvented gas fireplace that you use a lot.
Don't use it a lot as it gives off a lot of water vapor. Agreed the attic stair scuttle is likely awful leaky. What is the current humidity in your home ? Tape the perimeter of your scuttle until you address a more permanent solution.
Exterior is 39F and 98% humidity, Basement is 63F and 35% humidity, 1st floor is 70F and 36% humidity, second floor is 71F and 35% humidity. The fireplace has not been on today.
Would this be a sufficient product for the scuttle? https://www.walmart.com/ip/Energy-Wise-Attic-Stairway-Cover-25-x-54-x-11-R-Value-of-14-5-Attic-Stairs-Insulation-Tent/440694994
I believe that humidity should be kept closer to 20% than 30% to minimize the frost in your walls and attic. Pretty sure the Wise Attic people are greatly exaggerating the r value but air tight is more important. It should be as tight as a refrigerator/freezer door.
If you watch you should see humidity climb rapidly when you run the fireplace.
I had a similar situation when I first moved into our 1940's era home about five year ago. It has a hip roof and a walk-up attic. When we purchased the house it had a scuttle at the peak of the roof where the hips meet. When I re-roofed the house I closed up the scuttle and planned to insulate between the joists among other things (the end goal being to condition the attic). That first winter I had mildew develop on the underside of the roof sheathing. By February I ended up cutting ridge vents into the hips, air sealing the heck out of the sheetrock between the top floor and attic, and created a sealed hatch for the stairs leading to the attic. I haven't had any issues since then. I used Air Vent hip vents but you have to be really careful about how you cut the slots so you don't cut too much of the sheathing: http://www.airvent.com/index.php/products/exhaust-vents/ridge-vents/hip-ridge-vent. Coincidentally, Steve Baczek just wrote a good article on how to build a hatch for attic access. Here it is: https://www.jlconline.com/how-to/insulation/airtight-attic-access_o
Good luck.
Have a similar issue! The first link you offered goes to 404 Not Found. :(
Thank you!
I've read about those hip ridge vents Matt, I don't think that I'd install them at this time but wait until our shingles need to be replaced as there's some boards I want to rip up and re-support properly. In the mean-time, would installing vents be a suitable alternative?
As for the attic sealing article- that's an interesting build, I'd have to figure out a modification as I made the opening too close to the outer wall and therefore there's not a lot of height. I was hoping that tent product that I posted would be a suitable option for air tightness.
I can't tell from the link to tent whether or not it provides an air barrier or just R-value. I think air-sealing is important for your scenario. If the tent fabric provides an air barrier and the issue is how the fabric attaches to the surrounding air barrier (in your case I'm assuming this is either sheetrock, plaster, wood, or plywood) you could try an air sealing tape like one from Tescon or Zip. I don't see how the zipper connection could be air sealed though.
I got thinking more about that article with the air-tight box. Currently, what we have is a 52x22"~ drop-down ladder setup. I installed this so I wouldn't have to bring the ladder up when I needed access.
I installed this in the spot due to it being really the only option due to other things in the ceiling (lights, smoke detector boxes, the way the joists run). Unfortunately, you can see how close it is to the edge of the wall, it is going to make it difficult for me to build a foam insulated box or wood box similar to the article that was posted above due to the roof line 10" above that door closest to the wall.
I was thinking about removing that setup (if it's worth all of this work), and building more of a square entrance like that I originally had but have that box be on the end of the current opening, furthest from the wall. That way, I could build a frame around the sides of it to keep the insulation back, to line it with 4" of foam board (including the top) and then create an air sealed gap. Thoughts? Or should I move it out of my kids room and into the hallway (if possible- I'll have to look to see if there's room up there for it, there's a lot of PVC and electrical to contend with.
Bumping :)
By no means an expert on this; however:
First question would be: is the moisture in your attic coming from inside your home or from outside via the soffits?
Do you know, can test, your house's level of stack affect?
2. Does the roof venting ratios reflect what the formula says it should based on square footage for the ceiling?
There's gotta be an answer. Good luck, don't give up and if you solve it, share it here as we can all learn and that would be awesome.