Question Regarding Floor Insulation

wanttolearn

Hi-

I have three rooms in my house that are significantly colder than the rest of the house (in depth of winter these rooms are more than 5 degrees colder than the rest of house).  I have tried everything to fix the problem.  I have had additional insulation blown in to the walls, I have made sure the radiators work well, I have even replaced the windows in these rooms.

While the problem is a little bit better now as a result of these efforts, it is by no means solved.

Recently I noticed that all three rooms are located above unheated crawl spaces, while the rest of the house is located above a heated basement.  Could this really be the reason for a 5 degree plus differential in these rooms?  I always thought that heat travels upwards not downwards, and that "cold air does not rise", so I never bothered to consider the issue of these crawl spaces.  But some sites on the internet suggest that uninsulated crawl spaces can cause big heating problems for the rooms above.

I live in Long Island, NY, so we get fairly cold winters, but not brutal ones.  I have taken some tempearture readings inside the crawl spaces during winter, and it gets into the mid 40s, but generally not much colder than that.

It will be very difficult to get into these crawl spaces and to insulate them, so I am wondering if it is worth the hassle, or if it is a waste of time to try to insulate these areas.

Thanks for any feedback!

Steamhead

Do it

you'll notice a big difference if it's done right. I've experienced the same thing. I posted a thread about this some time ago, but some of the posts are scrambled and the pics are gone.



http://www.heatinghelp.com/forum-thread/108819/The-Hole-in-my-Bucket-gets-Smaller-Steamhead

Brad White

Radiant Cooling and Air Infiltration

Whenever you have a surface colder than the ambient air and especially cooler than your bare skin temperature, you are likely to feel cold.



A room with a 60F floor temperature where the room air temperature is 68F, is no different than when we try to deliberately cool a space using radiant cooling in the floor. A few degrees difference and the perception is cemented.



As Steamhead noted, insulation is the obvious and practical way to reduce (not eliminate but reduce), this temperature difference.



Another prime reason for feeling cold when all else seems to have been done or considered, is air infiltration, air leakage. On lower floors this tends to be higher in a house with more than one story, due to the stack effect. Sealing rim joists, edges of floors where they meet walls, electrical outlets (way down the list but easy to mitigate), all contribute to draft reduction. A blower door test arranged through your local utility or energy auditor may reveal things you have never considered before.



But air seal first. (Insulation sometimes, often in fact, prevents effective air sealing, which is the first step to a proper energy upgrade).

wanttolearn

reply

Brad-

I wanted to clarify that it is not just perception, but that these three rooms are actually colder than the rest of the house.  when I use a thermal gun to measure room temperature, some of these rooms measure at around 65 degrees when the rest of the house reads at 72.  i am talkting about the walls, not floor measurements. 

Is it possible that the uninsulated crawl spaces suck in so much warm air from the room above so that the rooms actually get so much colder by actual thermometer measurement?

i fully appreciate your comment as to air flows and cold perception, but this is a step further in that the rooms are actually colder.

by the way, on the topic of blower door tests, I have been tempted to have one done in the house.  are they effective and do they really give solid results that one can act on?

Brad White

Perception

The way I use the terms "perception" and "perceived" equals, "as experienced" and in no way says that what is experienced is not real or in any one's head. It is all used to describe valid observations by whatever senses are affected.



Believe me, I have no doubt the spaces are colder! I mean, when my company designs a radiantly cooled floor, the principles are the same as what you are getting for free (and not desired either!).



Because the floor is cooler, yes, it will absorb heat from your spaces, starting with your body in the room. (You are the proverbial tree falling in the forest. If you are not in the room, would you be uncomfortable? But the drain on heating energy will indeed affect space temperature and your thermometer and thermostat will pick up on that.



But the air leakage aspects are faster acting. A one air change per hour loss by air exchange speaks more than exchanging heat from radiation to surfaces then conducting these to the outside.



Properly done, a blower door test absolutely can identify where the leaks are. The primary output of a blower door test is a series of metrics such as your air changes per hour at 50 Pascals ("ACH50") your CFM airflow rate, (also at 50 Pascals, the most common benchmark pressure). The specific leakage ratio, your C factor (air leakage in CFM per Pascal differential), etc. etc. That is the easy and practically automatic part. I also get a reading on how large is the cumulative "hole" in your house, the sum of all leaks, rolled into one hole. A typical single family house might have 200 to 350 square inches of leakage area believe it or not. Picture a 30 inch wide window open between 6 inches and a foot, every hour of the day.



What I do when performing a blower door test is allow at least an hour of "leak hunting time". I set the blower in cruise control, holding a fixed pressure, usually 30 Pascals. Then I go around with the owner and, room by room, open and close doors to see which rooms tend to contribute more leakage both measured and felt by the hand.  The use of hand sanitizer is ideal as it amplifies the draft feeling on your hands.



For example, I start with all interior doors closed. I open one room and let the fan stabilize then record the CFM reading at that pressure as well as feel how drafty the room is with the door open a crack -subjective but necessary.  Then I close the door, move on to the next and the next, throughout the house. Certain rooms stand out that when open, the CFM rate increases beyond proportion.



So, I do follow a base protocol which is accepted almost universally (so your results can be compared to someone in Canada, Argentina or Australia with ease), but also identify the locations, often by feel. And no not forget the daylight test- shut off the lights on a sunny day in your basement and look for where the light leaks in. Can amaze yourself.

Roland_18

Cold Rooms

Hi All,

I have a kitchen that was by far the coldest room in the house. If the air temp was 68*, the temperature inside some of the cabinets was near 50*. Worse still, these cabinets are mounted on an INSIDE wall.

The problem turned out to be utility penetrations in the basement into the un-insulated inside wall. The contractors who installed the plumbing, waste lines, electrical, etc. really needed sharper saw blades or smaller gauge shot guns to make the penetrations.

The un-insulated wall was acting like a chimney, sucking copious amounts of air from the basement and living space, up into the attic. Hence the cold cabinet interiors. A few very messy hours with canned foam insulation took care of the draft and the cold kitchen. Also, make sure your weather stripping is in excellent condition.

I agree, make an effort to plug the air leaks before putting lots of cash into insulation.

wanttolearn

another follow-up

this is all extremely helpful to me, because all three of these rooms that I am refering to also have utility penetrations through them running from the crawl space through the house upstairs.  so maybe we are on to something here.

in the past i have read about air sealing and such, but i didn't quite believe that a fairly small penetration from the basement into a wall cavity could really have such an effect on the temperature of rooms above it.  can a little bit of air draft really have such a difference to a house?

if there are any further insight into the effectiveness of air sealing, i would greatly appreciate it!

Brad White

What Roland Said

Is entirely and demonstrably true. I have seen as many leaks "in the middle of a house", connecting basements to attics and even reaching out to above a porch connection.



One blower door test I did on a remarkably tight 1925 house (tight for the age and compared to what I see around here), with a huge air leaking chase behind the stove. The draft, under blower door conditions, moved newspaper on the floor. The air was being pulled down from the attic. Now, normally, that air would go in and up -you would never feel that because air leaving is not blowing across your person for the most part unless you are right next to it.



That one leak, when re-tested, proved to be about 25-30 percent of the home's leakage area, in one place. The attic top was capped with sheet metal and filled with fire retardant foam over mineral wool and caulked. It took an hour or so and probably saved the owner about $200 per year, probably more. The comfort improvement is immediate.

VictoriaEnergy

Raidiant and convective heat losses

You are dealing with radiant and convection heat

Radiant heat travels from hot to cold.  So just as you experience radiant heat travel down from a patio heater; heat from you and objects in the room will radiate heat down into the crawl.  The minimal insulation value of the floor assembly limits the heat transfer.   Increasing the insulation will make a big difference.  If you do, also consider adding some to the crawl parameter wall, since you don't want the crawl to start freezing in extreme weather.

Convection heat is the mass of air which tends to rise like a hot air balloon.  Air tends to exit the building through holes etc in the upper part of the building.  An equal amount of air is sneaking back in the lower part.

Brad wrote:  "But air seal first. (Insulation sometimes, often in fact, prevents effective air sealing, which is the first step to a proper energy upgrade). "  I couldn't agree more, but don't focus your air sealing to just the area over the crawl.  Also work on reducing the air leakage in the attic, around windows upstairs etc. too.

If your attic has vermiculite insulation in it; be aware some of it has naturally occuring asbestos in it. (google it)