home heating / efficiency questions

OK...so this is not ski-related "Tech Talk", but I always debate whether these "technical" questions belong in TT or PR. I always think PR is for ALL non-ski-related stuff.

Anyway...

(1) I've got a back room in the house that is mostly used as a guest room/storage. Most of the winter I close the door on it, put a towel to "seal" the door, and set the heat (electric) to 45F. The master bedroom/bath is above this room.

I realize that this is somewhat energy-efficient as I'm not paying to heat an area of the house that we're not using and I am preventing the heat from other areas of the house from leaking in, but....

a. Should I keep the temp a bit higher? If so, how much?
b. Is it essentially costing me more $$ to heat the upstairs bedroom because the rooms below it are "too cold"?
c. When we do prepare for guests, it takes a while for the rooms to heat up (first time). Obviously keeping it warmer (55?) would reduce this time to heat up and save some $$...but is savings given away by keeping the room at the slightly higher temp the rest of the time?

[I realize you need a thermal model of my place to really answer these questions. :)]

(2) This fall I insulated the crawlspace wrapped the pipes, and installed proper cross-ventilation. Presumably, this saves some money in that heat is not leaking to the crawlspace (or less heat is leaking there). I also put a vapor barrier on the ground.

The energy co told me to leave the vents open year-round...as long as someone is here, there's no chance of the wrapped pipes freezing.

Question: Should I ignore the energy co's advice and close the vents? Presumably, this could build up a little extra water (I would open the vents in the spring, summer & fall), but I'm wondering if closing the vents would keep the crawlspace warmer and even less heat would, then leak down there. Would it make any difference on the warmth of the floors?

Thanks much for any thoughts.

UpAN: My opinion is, you're going about it correctly. BUT.... What type of insultaion ? How much?

I'm no electrician or inspector, however, if you don't get enough advice from the board, let me know and I'll send a buddy over who can figure it out w/out chanrge.

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Originally Posted by schwerty

UpAN: My opinion is, you're going about it correctly. BUT.... What type of insultaion ? How much?

I'm no electrician or inspector, however, if you don't get enough advice from the board, let me know and I'll send a buddy over who can figure it out w/out chanrge.

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thanks, schwerty...the crawlspace is done (R30 batts + R11 fiberglass on the water lines + 6mil plastic on the ground) -- and it's up to spec for the energy co.

the energy co feels like the pipes won't freeze and that it is best to leave the vents open (i think they're worried about radon -- and they also think i might forget to re-open them in the spring which, i agree, would be bad)...but the question is really about saving $$ on heating.

i very much appreciate your reply.

If the back room is as insulated as the rest of the house, I would tend to leave it open and let the air move around. We have electric baseboard heat but only ever use it in one room...keeps the rest of the house fine.

The cold air below will definitely affect the comfort level of the room above.

radon is a scam, anyways

You realize that even 10 energy experts will have 8 different ideas about these questions...trial and error is the only real solution

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Originally Posted by RootSkier

radon is a scam, anyways

You realize that even 10 energy experts will have 8 different ideas about these questions...trial and error is the only real solution

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yeah...i'm not worried about the radon, esp if the crawlspace is only sealed from nov-april.

anyway, i do realize people will have different opinions and i could experiment. problem is that i would really need to do a comparison over one season vs. the next (or a minimum of at least one month to the next), and weather fluctuations could affect the results.

figured someone might know a better starting point.

I truly have no idea, but do live in a cold place (particularly cold as of lately) my answers are as follows:


(1)
a. No - If nothing is freezing keep it as it is.
b. No - Heat rises. Heated floors are fabulous, but it is not "costing you more".
c. Depends on how often you have guests. I suggest for good friends and family turning the heat up a bit and leaving the door open for about 4 hours before they stay. For casual stoppers by use the tried and true "sorry it's cold, we don't use this room often" method. Add alcohol and nobody cares.

(2) Radon is weird, have you tested for it? If you have it, keep the vents open or whatever they recommend. Otherwise do what you think is efficient. Your a smart fellow, go with your guts.

(2) Remembered I read something about this. YOur insulation will keep the crawlspace colder than before with increased risk of water pipes freezing. Closing the vents in the crawlspace should be fine if it's done just for a month or two, or when it get's really cold. Yout vapor barrier on the gound will help a lot on the moisture situaition uinder there anyway.

Cost effectiveness trumps efficiency. What are you paying?
Is electric power the lowest cost option (compare propane or natural gas).
Closing space from heating demand, saves energy and money. You are on the right track.
If you are not heating an area, you only need enough heat to prevent damage (condensation or cave syndrome, or pipe freezing).

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Originally Posted by RootSkier

If the back room is as insulated as the rest of the house, I would tend to leave it open and let the air move around. We have electric baseboard heat but only ever use it in one room...keeps the rest of the house fine.

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thanks...the space is as insulated as the rest, but isn't that simply paying to heat a space that i don't use (regularly)? i did install programmable thermostats back there so the temp will never drop below a particular setting; i have one setting for "vacation/empty/no guests", and another for guests (day/night).

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Originally Posted by Camel Toad

I truly have no idea, but do live in a cold place (particularly cold as of lately) my answers are as follows:


(1)
a. No - If nothing is freezing keep it as it is.
b. No - Heat rises. Heated floors are fabulous, but it is not "costing you more".
c. Depends on how often you have guests. I suggest for good friends and family turning the heat up a bit and leaving the door open for about 4 hours before they stay. For casual stoppers by use the tried and true "sorry it's cold, we don't use this room often" method. Add alcohol and nobody cares.

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thanks! i have no problem heating the rooms when people are here...it's just that i don't want to waste energy/$$ when they're not. i think in my trial run of how quickly i could heat the room, i left the door closed...when i really should have thrown 'em wide open. good call.

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Originally Posted by runethechamp

(2) Remembered I read something about this. YOur insulation will keep the crawlspace colder than before with increased risk of water pipes freezing. Closing the vents in the crawlspace should be fine if it's done just for a month or two, or when it get's really cold. Yout vapor barrier on the gound will help a lot on the moisture situaition uinder there anyway.

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yes, the crawlspace will absolutely be colder than before, which is exactly why i insulated the pipes. i had the work inspected by the energy co, and they felt that even in the coldest weather we have here the pipes will be OK as long as people are living in the house/running water periodically. the crawlspace will be colder, on average, but it will also never get as cold as (or as warm as) the outside air. (at least in theory)

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Originally Posted by Cirquerider

Cost effectiveness trumps efficiency. What are you paying?
Is electric power the lowest cost option (compare propane or natural gas).
Closing space from heating demand, saves energy and money. You are on the right track.
If you are not heating an area, you only need enough heat to prevent damage (condensation or cave syndrome, or pipe freezing).

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we have ultra-low electricity rates here, and most rooms have baseboard or radiant heating. i do have a propane stove in the main room of the house, but i try to use it less as propane isn't cheap. i did install programmable thermostats everywhere (except i haven't figured out a way to do it for the gas stove yet), so generally we're only heating the rooms we're in at the time.

these back rooms are currently at 45; other rooms are kept at ~58-60 when we're out/not in them...then the rooms we're in (except sleeping at night) are around 68.

is 45 OK to prevent damage? lower/higher?

should i try to keep all the room (except the back rooms) at a higher temp for efficiency? i imagine i'm always losing heat from the warm areas to the cold, so warm air is always flowing out to those rooms we're not in at the time. maybe the speed of the outlfow would be less if the non-occupied rooms were at, say, 64 instead of 58-60.

installed insulated (but not thick) curtains everywhere, have double-pane windows for the most part, and most windows have blinds (not a huge deal, but it helps a tad). i open the curtains/blinds to catch the sun & close 'em at night.

thanks again, everyone!

Getting back to (1), the lack of air circulation and low temperature can lead to mould and mildew.

In a past house I found 60 to be the minimum for living spaces. It all comes back to mildew and humidity. Cooler air holds less water vapour so as the temperature falls the humidity goes up. With cooking and showering the humidity goes up and when you set back the temperature the humidity goes up some more. Now you have a cool humid environment.

Older houses aren't airtight so there's ouside air exchange which keeps the humidity down.

I close my crawlspace vents in the fall and open them in the spring. I have no idea how that effects my energy bill.

How many walls of this room are exposed to the outside? Keep in mind that it's really the total surface area of the whole house that's exposed to the outside that determines heat loss. If there's only one exterior wall in that room, it wouldn't change your net surface area by much. If it's a corner room or an extension off the main house (3 ext. walls) then you're increasing the surface area a bit more. Also, how many windows? Windows are going to be the majority of your heat loss, but you can insulate them easily by building wooden frames with a sheet of plastic that fit in the windows and create a sealed airspace. So, if there's only one exterior wall, and few windows, I'd keep the the door open and heat it along with the rest of the house. If there's more walls/windows then keep dping what you're doing, but maybe keep the temp a little higher.

What Blue said, the exposed walls are the key to insulation. Usually cause they also have windows. Keep the door open and close the vents in the colder months. A lot of the heat lost from the room will just go up to the bedroom and simply keep the heat off upstairs.

Crawl space venting has recently become a hot topic of discussion among the ICBO crowd (building codes and such).

The current progressive thinking holds that if you seal the crawl space floor and stem walls with at least 6 mil plastic - then there is no need to vent at all since no ground borne moisture will intrude into the space. The whole idea behind foundation vents is centered on preventing moisture buildup in an enclosed space. Recent studies found that over 90% of said moisture came from the crawl space dirt floor rather than from outside.

If you already have vents - then once the space has been sealed with the plastic - close the vents over the winter to prevent airborne moisture from entering the area.

Note that sealing the space with 6 mil plastic means all seams are taped and the plastic is lapped up the side of the crawl space stem walls and taped to the mudsill plates (I also use Liquid Nails to bond before over-taping).

Another thing to consider is adding subfloor unfaced batt fiberglass insulation between the floor joists. After that is done - screw up 4x8 panels of 1 inch thick rigid foam insulation to the underside of the joists as well. Helps hold the insulation in place and adds up to 5 points of "R-factor" insulation value. Tape the seams of the foam board as well of course.

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Originally Posted by Snow Dog

Getting back to (1), the lack of air circulation and low temperature can lead to mould and mildew.

In a past house I found 60 to be the minimum for living spaces. It all comes back to mildew and humidity. Cooler air holds less water vapour so as the temperature falls the humidity goes up. With cooking and showering the humidity goes up and when you set back the temperature the humidity goes up some more. Now you have a cool humid environment.

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Thanks.

Are you saying that cold air holds less water (vapor) so that water gets passed on to walls, furniture, etc.?

During the winter (which is the only time this heating thing is an issue for us), our home's overall humidity is very low...around 25%. i'm getting a humidifier for the areas we spend the most time & sleep as I've heard we should be in the 40-45% range. Since I observe the in-home humidity dropping as temp drops, what you wrote is puzzling to me. Thanks for clarifying!

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Originally Posted by Big Blue

How many walls of this room are exposed to the outside? Keep in mind that it's really the total surface area of the whole house that's exposed to the outside that determines heat loss. If there's only one exterior wall in that room, it wouldn't change your net surface area by much. If it's a corner room or an extension off the main house (3 ext. walls) then you're increasing the surface area a bit more. Also, how many windows? Windows are going to be the majority of your heat loss, but you can insulate them easily by building wooden frames with a sheet of plastic that fit in the windows and create a sealed airspace. So, if there's only one exterior wall, and few windows, I'd keep the the door open and heat it along with the rest of the house. If there's more walls/windows then keep dping what you're doing, but maybe keep the temp a little higher.

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Thanks, BigB--The room in question (the one closed off) has 2 windows and is in a corner of the house. Windows are double-pane glass w/ blinds & curtains. Maybe I should insulate the windows a bit better there...but that's the same way i insulate all the double-pane windows in the rest of the place.

Sounds like there's a fair bit of surface area, so heating those spaces would represent a significant increase.

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Originally Posted by Parvo Pup

The current progressive thinking holds that if you seal the crawl space floor and stem walls with at least 6 mil plastic - then there is no need to vent at all since no ground borne moisture will intrude into the space. The whole idea behind foundation vents is centered on preventing moisture buildup in an enclosed space. Recent studies found that over 90% of said moisture came from the crawl space dirt floor rather than from outside.

If you already have vents - then once the space has been sealed with the plastic - close the vents over the winter to prevent airborne moisture from entering the area.

Note that sealing the space with 6 mil plastic means all seams are taped and the plastic is lapped up the side of the crawl space stem walls and taped to the mudsill plates (I also use Liquid Nails to bond before over-taping).

Another thing to consider is adding subfloor unfaced batt fiberglass insulation between the floor joists. After that is done - screw up 4x8 panels of 1 inch thick rigid foam insulation to the underside of the joists as well. Helps hold the insulation in place and adds up to 5 points of "R-factor" insulation value. Tape the seams of the foam board as well of course.

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Thanks, PP:
I have 6mil plastic on the ground...but seams are not taped nor is the plastic taped to mudsill plates.

I did put subfloor unfaced batts in (r30); they are held in place with some thin strips of wood. sounds like your solution would improve insultation.

Interesting points about closing the vents. Officially, the energy co must say keep them open for radon, which may just be CYA. Sounds like I could afford to, probably, close the vents in the winter with the solution i've got....and FOR SURE could close them in the winter (or may be forever) if i seal all the seams down in the crawlspace.

Thanks!!

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Originally Posted by upallnight

Are you saying that cold air holds less water (vapor) so that water gets passed on to walls, furniture, etc.?

During the winter (which is the only time this heating thing is an issue for us), our home's overall humidity is very low...around 25%. i'm getting a humidifier for the areas we spend the most time & sleep as I've heard we should be in the 40-45% range. Since I observe the in-home humidity dropping as temp drops, what you wrote is puzzling to me. Thanks for clarifying!

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In weather reports they mention the dewpoint -- the temperature where water vapour condenses to water. The same thing happens inside. If the humidity is high and a wall is cool some of the vapour will condense making the wall feel damp. If you take a cold glass out of the fridge, water will condense on the outside if the humidity is high enough.

I live on the coast at the edge of a rainforest so the outside humidity is high all the time (it's 94% right now). According to my humidistat my inside humidity is never below 50%. In Wyoming mildew might not be an issue. But it's something to keep an eye on.

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Originally Posted by Parvo Pup

Another thing to consider is adding subfloor unfaced batt fiberglass insulation between the floor joists. After that is done - screw up 4x8 panels of 1 inch thick rigid foam insulation to the underside of the joists as well. Helps hold the insulation in place and adds up to 5 points of "R-factor" insulation value. Tape the seams of the foam board as well of course.

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But make sure that you don't create a vapor barrier on the crawlspace side of your floor. You want moisture to be able to travel out of your insulation on that side. The vapor barrier should always be on the warm side of your insulation.