How to best heat an attic with plumbing running through it?...

wcweaver3

Hi. I recently purchased a one-story, slab home, built in 2010, in the Atlanta metro area. They originally built the home with the plumbing in the concrete slab, but there was a flaw in many of the homes in the area, which caused the pipes to fail with catastrophic flooding. The fix was to re-route all the plumbing through the attic. This is an open floor plan with the gas furnace in the attic, so the attic areas over the living spaces are very well insulated. The areas over the non-living areas, such as the garage, are uninsulated. The re-routed pipes in the attic are PEX pipes with standard foam pipe insulation around them. The pipes over the heated spaces disappear into the insultation. But the pipes, with foam insulation around them over the garage, are essentially just exposed. See pictures.

The Atlanta airport last night and this morning reported the following hourly temperatures 11pm to 11am this morning - 32,31,29,28,28,27,26,25,24,24,26,30,39. Last night, I put a remote temperature sensor near the farthest pipe above the unheated garage, closest to outer wall. At 6am this morning, the outside temperature was 29, the garage temperature was 48 and the lowest temperature during the night the remote temperature sensor recorded near the pipe in the unheated attic above the garage was 32. How long the freezing temperatures lasted in my attic above the garage, I don't know, it just records the lowest temperature encountered (the remote sensor is shown in the first picture below).

While cold spells like this in the Atlanta area aren't common, they do happen, and it has been known to go down into the teens with howling winds.

I do the normal types of things when it gets colder such as let pipes drip, open cabinets, etc. However, the recent cold front blew in while we were away, and we couldn't do anything more than crank up the heat in the house using a remote thermostat.

As I am a cost conscious, belt-and-suspenders kind of guy, I think I'd like to do something to try to get ahead of a potential frozen pipe problem. I am thinking of the following fixes…

1. Electric heat tape around the pipes. To me, as a DIY guy, this looks like a lot of work and a real pain to do as I have lots of pipes running all over the place in the attic space. And, I'd have to work around the current foam pipe insulation.
2. As I have the furnace in the attic, open up a vent in the attic ductwork to vent hot air into the attic space. Probably not a really efficient solution and if the living space is warm and the uninsulated attic isn't then I might be sweltering just to get the attic a couple of degrees warmer.
3. As I have power in the attic, buy a $40+ radiant heater (not an electrical resistance heater) at one of the big box stores, set the thermostat on it at 40 degrees and be done with it.

I like option #3 the best, but I don't know if I have missed any other options or if #3 is practical and will get job done.

Any guidance is most welcome. Thank you!

EdTheHeaterMan

This is a common issue for many of those Yankees from above the Mason Dixon.

I used to live in NJ where this needs to be addressed regularly. But I'm one of those Damn Yankees that came south and stayed to live here. LOL. I have the same home on a slab with no place to put the replacement plumbing except in the attic. When it was time to replace my plumbing, I elected to open up the walls and keep the pipes below the attic insulation. Your repair didn't use that option.

I am not a fan of electric heat tape. Although rare, there are cases of that electric strip overheating and starting a fire. I just don't want to be one of those rare cases. Another option is to have the roof insulates with spray on foam. that will put your furnace and ductwork inside the conditioned space. The air conditioning cost will drop drastically and if you need a repair in the summer, the workers will have a more comfortable work space.

Your option #3 is not fool proof and any electric heat from a big box store will be electric resistance. If it is the oil filled radiator type or the ceramic radiant or any other electric type, the source of the heat is from one of those electric resistance heaters and they should not be in a space that is not monitored regularly.

#2 option is the safest way to do it but not the most efficient. You could get a thermostat that is set for 36° to open a damper on the furnace to let heat in the attic when needed. That will be a little more efficient.

EBEBRATT-Ed

This option from @EdTheHeaterMan is the best solution in my opinion.

"#2 option is the safest way to do it but not the most efficient. You could get a thermostat that is set for 36° to open a damper on the furnace to let heat in the attic when needed. That will be a little more efficient."

Voyager

Given the rarity of sub freezing weather in your area, I would go with option two. Put an electric damper on a central supply duct that you can either open manually with a switch during the rare times you need it or with thermostatic control to run automatically.

TheUpNorthState88

I do have some plumbing in my attic. My home still heats through a gravity hot water heating system. In my attic is my expansion tank which still has water expand up to it when the system runs and a little sits in the tank at all times. I also add water to the system up there. The previous owners wrapped it in used carpeting which I removed. I recently had my home rewired to remove the old Knob and Tube and had my electrician install power outlets in the attic, which includes one GFCI outlet next to the area of my expansion tank. This year (my second winter in the home) I installed heat tape around the whole tank and piping under it. And then wrapped the tank with unfaced pink fiberglass insulation.

The instructions say to insulate the pipe after it has been wrapped hence the fiberglass. It has a built in thermostat that once temps dip below 38°, it turns on. I also have the tape plugged into a smart plug (with energy monitoring) just so I can monitor when it is on. Make sure not to get the cheap off-brand stuff from Amazon.

Make sure to get a UL or Intertek listed one. Pictures of my attic expansion tank area before and after wrapping it all up.

**Fyi: those looking at these pics, yes, there are water spots seen, those are remnants from past roof leaking before a new roof was put on by previous owners. I also keep a tupperware under it along with a leak detector. That tupperware is there to buy me some time if the leak detector ever does alert me and I am not home. It has already save me $1000s in damages when it alerted me the old valve DID start leaking last year (tightening the packing nut fixed that).

hot_rod

Wow! an old riveted tank.

A shocking looking sink, is that a ground wire on the trap arm?

Larry Weingarten

Hi, There may be an option #4. It would be converting the attic to conditioned space. Start by sealing off vents… now insulate under the roof. The attic is now kept warm by being attached to the conditioned space. As long as heat loss from the roof is less than the heat transfer up through the ceiling insulation, you win. Here's something on this from Building Science Corp. https://buildingscience.com/documents/reports/rr-9701-measurement-of-attic-temperatures-and-cooling-energy-use-in-vented-and-sealed-attics-in-las-vegas-nevada/view

Yours, Larry

Geosman

I might suggest creating a cardboard dam on either side of the garage water lines and filling the space around the water lines with cellulose insulation. Cellulose is far more denser than fiberglass and will maintain the water lines above freezing for a much longer time than will fiberglass. In my humble opinion fiberglass makes for good air filters and will allow for convective air movement through the insulation whereas cellulose is dense and prevents convective air movement. Homes that I have worked with that used blown cellulose overtop of existing blown fiberglass insulation found their heat retention in the winter to be superior and summer heat transmission to the rooms below substanially reduced. Most all cellulose insulation is treated with borates which provides both fire resistance and insect resistance. Borate is the only natural substance that cockroaches have noever developed a resistance to so good by to the fall lady bug infestations trying to find a warm space in your attic.

bill_brooks

i had a tenet bathroom that was plumbed with the supplies passing over an unheated stud cavity. the pipes

were well insulated. however, when the temp. dipped below 0deg occassionally ….. no bathroom plumbing.

i purchased an oil-filled radiator, removed the casters, and bolted it to a platform bridging the joists.

because the rad was slightly below the plumbing as it travelled into the bathroom floor, convection heated

the space nicely. i wired a lo-temp. stat/w recepatcle so the rad only came on when the surrounding crawl space approached 40deg.

what made the fix possible was the rad. being located above a suspended ceiling. this gave easy access to

check on things.

RobertJordan

Expanding on Larry Weingarten about turning it into conditioned space - Doing so keeps the ducts in conditioned space so you aren't losing heat to the cold attic. Especially important if you have AC and a 150 degree attic in the summer. How leaky are your ducts?

Spray foam is the usual way. Advise a couple inches of closed cell foam on the sheathing to avoid possible condensation on the sheathing.

scott w.

I am further south, down the peninsula than Atlanta. Had a firm do the spray foam on the attic sheathing, Made a world of difference in the cooling bill. Was told the temperature in the attic would only be a 10 degree difference from the rooms below. The firm completely sealed the attic off with foam so no outside air intrusion in the attic space. I highly recommend that option. Your heating and cooling bills should see enough savings to pay for the insulation job.

Haven't seen one of those old sinks that TheOldNorthEastState88 has in his attic for years and years. My grandmother had one of those trough sinks in her old vintage kitchen with a hand pump on one end that used to pump the water up to the sink from the cistern.

wcweaver3

Thank you all for the great comments - @EdTheHeaterMan @RobertJordan @Geosman @scott w. @Larry Weingarten @Voyager@TheUpNorthState88@bill_brooks

I really enjoyed seeing the riveted tank as well as reading article about the spray foam on the roof decking for the homes in Vegas. While it isn't practical to turn the attic area above my garage into a living space (too small and not enough height), I think it's very doable to turn it into a tighter air space. My house was built in 2010 by Pulte and this attic space is very leaky - lots of attic eve vents with a standard radiant foil barrier on the underside of the roof decking. Lots of insulation above the heated parts of the house, but none over the unheated garage where the water pipes are (the pipes also run above the heated parts of the house, but they disappear under the insultation). I think option of tapping into the supply duct is the best (option #2),but will pursue the cardboard cellulose dam around the pipes. Additionally, as my cooling bill is going to be way higher than the heating bill as I am now in Atlanta, I will pursue getting a contractor in here for the spray foam option. @bill_brooks I thought about your idea, A LOT, before you mentioned it and would have hooked it up exactly as you mentioned. What low temp stat did you use?

EdTheHeaterMan

I agree with @wcweaver3's comment on the expansion tank. It is riveting

Larry Weingarten

Hi @wcweaver3 , Being in Atlanta, you also have Allison Bailes with Energy Vanguard nearby. He does building science for a living, and is a good guy.

Yours, Larry

chris_nj

My friend had the same problem we are in nj so quite colder here. The homeowner insurance made him use a company otherwise we would have done it. They ran all pipes in PEX in attic and left. I go up there they didn't insulate anything so we did. We used the really soft foam insulation I forget the name and taped all joints so far after about 7 winters no frozen pipes. The one thing that might make a big difference is I installed the watts hot water recirculation system that uses the cold pipe as the return so I think that helps a lot. Maybe a double benefit for the pump system.