Crawl space insulation

As with a lot of the other posters I think that the spray on stuff is quite good for the underside of the roof. I had it done on my old house and heating was reduced by half the following year (they also replaced a couple of broken tiles which may have helped)

For an eco friendly alternative to rockwool/fibreglass insulation (I hope that you understand the stuff I'm talking about) for between the floor joists e.t.c. try the wool based products. Yes they are a bit more expensive but they also have a much higher thermal insulation property then the same thicknes rockwool product.

 

Of course, if I lived in an area where termites and/or carpenter ants thought of my house as a potential food source, I'd not only have a concrete slab, I'd have poured cement walls

Beaver Plastics Logix insulated concrete form blocks

The Insulated Concrete Form or ICF has been popular here for awhile to build basement walls. More recently, to dramatically improve home insulation performance and strength, ICF has been applied to structural walls too.

The home at my hobby farm was built this way, the walls finished width are around 12 inches. Compared to regular 2x6 studs, far superior insulation and much quieter

 

You have to be very careful in your approach to projects like this. It is similar to attic issues but with several other potential problems:
1. Your water lines in that area are kept from freezing by the duct and flooring heat losses. (More on this later.)
2. In many areas you do not want insulation to cover concrete reaching from the ground to the rim joists, etc. because it makes a non-visible conduit for termites or other bugs to exploit.
3. Moisture against the wood is bad. Moisture under the house is bad. This was a major issue in the Southeast. Things can get really sour if it gets wet under the house.
4. The vents are there to produce air circulation and thereby prevent condensation.
5. Radon is a concern in some areas.
6. You might even be pulling some combustion air through the space if you don't have a sealed, direct venting furnace. (This has me stymied on sealing up some gaps from unheated spaces into the utility room.)

My suggestion is to talk to local builders about how they construct new homes. City inspectors might also be able to answer questions about what will and won't work (they've probably seen many failures.) Ask about current standards for insulating the floors and ducts, and if they insulate the water lines or where they locate them so that they won't freeze.

While I don't have a crawl space anymore, I've addressed the water line issue recently as I insulated a sub basement storage space wall to improve the comfort of the adjacent room. I also insulated most of the duct running through the unheated space. (I did not insulate the ceiling/floor above however.) By my calcs and measurements I concluded that the unheated space could now drop below freezing at an ambient temp somewhere below 0 F. This was an issue as my water line enters the house here and at least six feet of water line are exposed.

I chose to install a tape heater on the water line that kicks on when the line reaches 38 F and shuts off at 45 F. It's averaging about 5 Watts for the 6 feet I added with ambient temps running 0 to 30 F most of the time. Since it pulls about 40 Watts when on it appears to run about 1/8th of the time at these temps. I will need it about 3 months each year.

Another solution to consider would be putting in some sort of simple thermostat to open a register from the duct work into the crawlspace whenever the temp reaches some threshhold. This of course "wastes" energy, but it might be a necessity to prevent lines from freezing in the coldest weather. (One could also use incandescent light bulbs in such an arrangement--like we used to do in well houses when I was a boy. It would be best to use two bulbs and some sort of thermostat...a single bulb burns out too frequently in my limited experience with frozen water lines.)

Regardless, seal the ducts and registers. Air leaks from the ducts were NOT intentional parts of the design to add freeze protection, so there should be no potential freeze concern in doing so. Most guides say to use mastic for sealing, but I've only used GE Silicone II sealant on mine. I've not been at all impressed with any of the tapes I've looked at or tried.

Insulating with batts between joists sounds like a good bet (after air leaks are sealed) but you would still need to be sure that you have addressed any potential freeze issues. You will need those wires to hold the batts in place. I'm not sure if you should get unfaced batts or faced. If you use faced then you want the vapor barrier against the heated space (floor.) If instead the face is place out, then there is concern that moisture will be trapped in the insulation/against the wood. I second the recommendations about goggles for overhead work--you will want ones with some venting though as they tend to fog anyway. I used a disposable white coverall (bunny suit) and a respirator to do my insulation work.

Bounce your plans off some professionals in the area just to make sure you aren't about to do anything silly. (That's what I try to do anyway.)

 

jayman,

I've also read that sometimes the aggregate used for concrete can be a source of radon.

 

True enough around here, the granite sources of agg can release some Radon. A common additive that has been able to dramatically reduce this exposure is silica fume, or micro silica

 

That hasn't been an issue here with iso spray foam. Though our termite issues are very small compared to the southern US

The blue iso spray foam is approved as a vapor barrier. If you spray it over the joists, it will actually protect them from condensation.

If you get a chance to watch Holmes on Homes, he discusses how well the blue spray foam works to protect the structure from condensation and mold. He has a plug for their product too

Make It Right? | Video Player

According to the EPA map, in most areas

http://www.epa.gov/iaq/radon/pdfs/zonemapcolor.pdf

At one time, house construction allowed the use of combustion air from the space, not from dedicated sources. There is a huge risk of CO if the house is suddenly sealed up

Here, a dedicated combustion air pipe is required, and/or a direct vent appliance

 

You got most of it right,

A couple of comments,,, Foil faced or Paper faced batts should ALWAYS be installed vapor barrier side TOWARDS the heated space. If you find that someone has installed it backwards,,, instead of taking it down, you can slice the vapor barrier with a utility knife in a bunch of slits to allow vapor to escape.

Fiberglass batts can be held in place with spring wires that are cheap and easy to install, but I prefer to follow the wires with lathe nailed between the joists. You can also staple a layer of Tyvek or some other air infiltration barrier under the fiberglass to reduce cold air infiltration.

As for foundation venting, your local inspection authority as well as local builders of good repute should be your guide. Radon should be monitored with a cheap monitor, and vented as needed.

The issue of using wasted heat from duct work to keep the pipes from freezing is crazy. (Although keeping the pipes from freezing is a real concern. Pipe insulation of proper thickness should cover all under house plumbing. (I have insulated under house pipes to keep pipes save at -40) It is cheap and easy to install, so to waste space heat when a simple pipe wrap will do, will save a ton of energy.

The object of the exercise is to use as little energy as possible.

Icarus

 

The problem I have with relying on insulated pipe is that if the pipe sits long enough with no flow it will freeze despite the insulation. It all comes down to where the heat sources are and how long the temperature is below freezing. Without flow, the insulation is only a time lag and you are relying on thermal mass to save your a**. (Sorry, but that rhyme was irresistable.) Wrapping a bottle of water in insulation and putting it in the freezer will only slow down how long it takes before it bursts. It is probably okay in many circumstances because of the geometry of the runs and lengths run into heated spaces (conduction or even some convection inside the pipe) or warm ground. And for some it might not be catastrophic to have a line rupture. Depends on what you are comfortable with risking and what damage will occur.

I'm not familiar with all the types of radon control, didn't realize that there were residential continuous control systems that were turning off and on. I have one that runs 24/7 with no continuous monitoring. I wouldn't advise anyone to put this on radon level control for several reasons. First, you aren't going to measure (control) radon at all locations in the space anyway so you really don't have a sound basis. Second, if you have enough radon that you need to control it this isn't "1.9 is good, 2.1 is bad." Both are a problem. That would be sort of like saying "1.9 packs of cigs a day is okay but 2.1 is too much." Better to let the system run, pulling levels down constantly.

 

Shawn,

You are right about insulating pipes only delays how long it takes to freeze. In most cases, either a circ system, or leaving a little water dripping in the far faucet will keep lines from freezing indefinitely. In most houses, most water lines are used daily. I have insulated an incoming water line @-40 that only gets used once a day. There are "arctic" closed cell foam that will insulate a 3/4" to R-20. There also are a variety of semi-conductor heat tapes that draw no wattage until the temp reaches ~40f and then they generate heat only as needed. At full on (which they never are~) they draw 3-5 watts per foot. They are approved for use on plastic pipe, and UNDER pipe insulation,,, some can even be installed INSIDE a pipe. Like I said in a previous post, using waste space heat to keep the pipes from freezing is very wasteful.

Frostex and Wintergard heat tape price sheet, heat tapes custom made to specifications. Buried water pipe heat tapes also.

As for Radon, we used to put a monitor in the cabinet drawer of new houses and checked it 6 months later. If radon was detected we would then do a continuos power vent in the crawl space. Crawl spaces are easier to deal with than basements.

Icarus

 

The problem areas are about 50% and in them about half of the existing construction would have failed by standards when radon monitoring was just beginning. Wasn't an issue for me until I moved back into this zone.

My understanding is that the passive mitigation design considerations in new construction largely eliminate the need for active mitigation systems.

Tell me about it... Farther north they've been more pro-active in this regard as I noticed when I came across Minnesota's standards. I'm not sure what the new construction standards are locally, but 90's construction here was still allowing combustion air from inside the home without dedicated combustion air lines. This seems to be a pretty poor idea for areas with real winters.

When I was looking over my furnace I noted that it had no dedicated air supply. Then I realized that it was in a utility room that had no vent grates either. It's a reasonably large utility room...but not that large! Essentially the furnace and water heater are pulling all of their combustion air through the joist spaces above, as well as from some gaps into a storage area and the garage. (And of course the dryer is in the room as well...so when all three are running...) I'm not sure if the area was enclosed after initial construction or not--if it was enclosed initially this never should have been allowed.

I put my CO monitor in the room. I probably should add a grate through an interior wall that would pull from the much larger interior spaces. This would have the advantage of pulling colder air near floor level rather than warmer air from above. I've held off on the grate so far while considering an upgrade to a condensing furnace, etc.

 

There are simple formulas for combustion air. How many square inches of air required for X number of Btus of burner. I don't have one off hand but I'm sure you can find them on line. Turns out, it is way more air than you would figure.

Icarus

 

Of course, one thing else to keep in mind is that a lot of those older homes are poorly insulated by current standards. When we first started to really tighten up our homes, we were creating a lot of problems

Eg: 2x6 walls, vapor barrier tuck-taped at all the seams, acoustic sealant at sill, tight doors and windows. We created a virtually air-tight house, with no consideration whatsoever on how to properly ventilate that home

For that reason, I expect we will see a lot of issues from homes built from the late 1980's to around 2002. Not only with stagnant indoor air, radon, but also mold issues.

I think just the use of HRV's in a lot of new home construction has gone a long way to helping in that regard. This is now my third home with an HRV, there is no way in hell I'd do without one now

Homes built a lot looser and draftier could probably get by with just the drafty windows and doors. Now that everything is so tight, we're even seeing more CO cases, some tragic.

If I recall, there was no code requirement here for dedicated combustion air supply until around 2000. You now require a 4 inch dedicated pipe

It still isn't done right, however. This climate can dip to -40 in winter, and we get snow too. A direct vent condensing furnace is allowed to poke out the side of the house, between the joists. That's a really dumb idea

Typically, that means the furnace combustion and exhaust are no more than 18-24 inches above finished grade. Yet, with the wind just right in a blizzard, you can get snow drifts 2-4 feet up against a house.

The *proper* way to vent a direct vent condensing furnace is out the top of the roof. You never have to worry about snow drifts that way, and indeed if you read the furnace installation manual, that is one of their more preferred methods anyway

Another flub - the HRV exhaust and intake hood vents are also poked out the side of the home, again no more than 18-24 inches above finished grade. Unless you have a bi-level, then the vent hoods could be as much as 3-4 ft above finished grade

Whenever it gets bitterly cold, say -30 C and colder, there always appears to be a "ground fog" of actual ice crystals. I've noticed my HRV intake hood, which has a screen, *always* ices up in -30 and colder. The HRV will then attempt to exhaust indoor air, but cannot draw in outdoor air

The "solution" is to get your butt out there and use a snowbrush to brush the snow/ice off the intake hood. At -40, that could be up to three times a day

A better solution is to locate the vent hoods higher up. My attached garage has a direct vent heater made by Reznor, the intake air hood is around 10 ft off the ground. It has never shown even a hint of icing or clogging

Just as builders up here pissed and moaned when the first energy codes were passed, I'm sure they will piss and moan if more changes are made. If it was up to them, they'd use single pane windows, recycled cardboard for insulation, 2x2 walls, and shingles barely good enough for 3 years

 

this thread has been very informative.....but has me scared that im in the process of buying my first home.

 

Hire a "good" pre-purchase building inspector. The few $100 you spend will be well spent. I don't know how you define "good", bug get some recommendations from someone you trust. IMHO too many "inspectors" are in bed either with the realtors, the pest control industry, or the banks. I would find someone who worked in the trades for a good number of years, retired builder or ICBO building inspector.

Icarus

 

I insulated the ceiling portion of the attic and a few walls with R-Max (R = 7.5 per inch) - a foil-faced rigid foam. I cut it with a hand saw to fit it between the joists. The space between the joists (2 x 6) is now R-50. I added to fiberglass attic batts to bring the ceiling insulation to R-100. Actual space taken up is less than 24 inches. Working in the attic is not fun and not something you do in summer, but the effort pays back many fold.

Some will say R-100 is impossible, but then they did not do the work nor do they understand the R-values of the foil-faced rigid foam. What to do when you make a mistake? Duct tape and foam. The biggest pay off is in the summer heat. The attic does not radiate or reradiate heat into the house interior. The house is very warm in winter, very cool in summer - without using the HVAC!

I did the work myself. I could not hire anyone to do this detail work, nor would they understand what I did. I worked with Rocky Mountain Institute concepts and guidelines. Contractors have come by and exclaimed, "R-100? Impossible (thinking of conventional insulation methods and space). Pay back or break even time period (compared to neighbor's utility bills): 2.5 years. Very cost effective.

I've caulked every crack I could find with 50-year caulking. Caulking also eliminates insect intrusion into interior. The front door is an air lock. The windows triple pane, interior is ceramic tile floors in central hallway, kitchen, bathrooms and porches (thermal mass). "Warm windows" - 5-layer insulated curtains or roman shades cover windows. Two sun piped provide 1500 watts of diffuse light at solar noon (sun scoops enhance low angle winter sun) and do not gain or lose energy.

Front porch is an "air lock" (double door entry). There are 11 windows and two large sliding glass doors. Sliding glass doors are double - one set of dual pane, a large air space with a ceramic tile floor, and an outer set of dual pane. We can open curtains in summer or winter for light, but stay warm in winter and cool in summer. I fully insulated and finished the garage (roof and walls) - stays cool in summer, warm in winter, and does not reradiate heat to house interior.

Overkill? Perhaps, but gas & electricity bills for last 20 years average $30 per month while surrounding homes pay $300 to $800 per month. You can put the money into the window one time or you can throw the money out the window every month. Unforeseen benefit - house is super quiet.

2300 ft2 house has an Energy Efficiency Index of 0.9 (superior). A HERS audit should produce similar results. House will command a higher price at the time it comes to sell the house.

 

Nice job Skruse!

Icarus

 

It's no problem, I pulled values from the equipment manuals for both. Probably could have done it using my old process high pressure boiler manuals if needed but wouldn't have had anything practical to compare against since I don't know the residential basis assumptions for DP.

It is a lot of air and points out how leaky the house is even after considerable tightening of the worst offenders. I'm pretty good at detecting combustion and draft issues (boyhood wood heating and wood cookstove cooking as well as industrial boiler experience) and this system has given me no trouble so far...which indicates how much air infiltration I have hidden behind siding, rim joists, window trim, etc. It's a good news, bad news story.

 

Yep, it's a system wide issue. Folks from one or two decades ago built and designed for rather loose HVAC, high air infiltration, and modest energy efficiency. As one tightens, things that had not been an issue before suddenly move to the forefront: mold, combustion air/CO, water lines freezing, radon, etc. It's almost like starting the design from scratch.

Haven't studied them yet, just another thing I need to investigate. If I understand correctly I doubt it will help with my current ventilation since there is no practical fresh air draw (essentially recirc.)

My big concern with 30 feet vertical interior is a recirc for cold/hot air from bottom/top respectively. I'm presently working out a new bottom return leg (presently a large room with NO return) as well as two registers to be placed in the far corner of two levels.

Depends on topography and home siting. I'm on the edge of ridge so my combustion air in the walk-out's ceiling joists would pull/expell at about 10-12 feet from grade. If I ever get a drift that high I'll have bigger issues (and likely be using a generator to run the furnace blower and ID fan, perhaps shooting the squirrels for gumbo meat.)

I don't think that will work for multi-level. The condensing furnaces don't have much draft because of low flue gas temps. This gives them little "buoyant" driving force and will result in additional condensation back down the stack that could be really problematic. I've got ~25 ft of vertical through my existing stack and figure I would have to relocate it to a lateral run out the utility ceiling joist (about 4 feet vertical from the furnace.) Hey, I could be wrong since I've never set up one of these systems before, but I figure my existing vertical run is a complete nightmare for a good condensing unit.

That's true of builders everywhere. Change is costly and it means painful (read "expensive") learning experiences. Plus their sub contractors will piss and moan and want more money/be set in their ways. I can't really blame them, but that doesn't mean that change isn't best or necessary.

Enjoying the discussion with you, icarus, and others. There is still a lot for me to learn. The different climates and different experiences are helpful.

 

Don't be afraid. Even if you think you have it all worked out things can be askew. Go into it with your eyes open and if you miss something, chalk it up as a learning experience. It won't be perfect so you need to keep a cash cushion in mind for some sort of major expenditure.

Take a close look at windows and HVAC is my recommendation. My inspector didn't really comment on the deficiencies of the HVAC. It worked and that was good enough for him. It probably would satisfy most folks, but I'm a picky SOB who wonders why the inspector didn't notice that the condensor was ~8 degrees from level. (Of course I wonder why I didn't notice that as well...except that I was focused on less infastucture type matters in my brief time evaluating the home.)

Granted, an inspector only has so much time, but you are paying for experience which should hopefully get them to focus onto the likely problem areas.

If I had it to do over again I might want someone with more of an HVAC efficiency rating background. To me, HVAC is the heart of a home. (It is the biggest operating expense.) Drafts suck. If I can't use every room year around in relative efficiency and comfort then I need to discount for that lost space. (I still really like my house, so I'm glad nobody frightened me away from it by telling me the HVAC system sucked. I'm still operating under the potential illusion that I can fix any major deficiency...)

 

We replaced two of our three oil fired furnaces with high efficiency natural gas models (it's a big building, but that's another story). The new furnaces are direct vent models with outside combustion air. As jayman describes, they are vented out the side of the house. I have to go out once in a while and remove snow from around the vent and intake. The good news is that they have combustion air sensors and will shut down if outside air is blocked. The bad news is that it gets very cold if they do that.

Tom