How to Improve Home Energy Efficiency and Reduce Costs?

Insulate the attic ductwork.

The attic return duct is insulated with fiber board with 1.5 inch fiber board. It is pretty old. Should new insulation be put over it or the old replaced? The supply ducts are a problem as by the time warm air gets to the other end I can't even feel the heat in the winter, and by the time AC air gets to the other end in the summer, I can hardly tell that it's been cooled. Is there anything that can be done to insulate an in-slab round duct of 6"-8" round?

I would replace the old insulation with new. It sounds like your heating and cooling your whole slab - which is a little surprising to me as I thought concrete was a pretty good insulator.

I think you're right about replacing the insulation. Do you know if it is best to use the highest R-value I can get, or is there a point of dimminish and return. Regarding the floor ducting. I don't know if cement is typically good or bad as a heat resistant material. It seems like it can sure absorb and get rid of a lot of heat. Possibly because these ducts are only a foot or so from the edge of the slab so heat transfers into it the summer and cold into it in the winter, thus reducing a great deal of the insulating capacity of the concrete. Also, when I bought a new 3-ton AC unit a few years back and complained about its ability to cool my house (I expected better than the old 2.5 ton), the HVAC company doing the installation checked temperatures in various locations. They found that the AC unit was cooling slightly more that 20 deg.F at the exit of the coil, and only about 20 feet away at the first register, the cool air had gained 8 deg.F. Of coarse, this was a 95 deg. day. Know of a way to insulate pre-formed concrete enclosed ducts? We also have to let the hot water run for quite a while to reach the kitchen sink about 40 ft. away.

Short of a complete redesign and replacement of your duct system, there isn't much you can do to improve the efficiency of your system. There are two or three things I would suggest you look at that might help. But, first, concrete is a fairly GOOD conductor of heat. A 4" slab will loss about 1 BTU/ sf ft/ deg F temp difference. And with its high mass (140-150 lb/cu ft),it will aborb a considerable amount of heat. However, if the base under the slab (gravel or sand base and vapor barrier) has been properly prepared, the heat loss into the ground will be minimized. Once the slab comes up to temperature, the heat loss would be less. Now: 1) Most likely the attic insulation was 'blown in' during construction and has settled. You could add fiberglass batts on top of the existing insulation. 2) Chances are the perimeter of the concrete slab was not insulated, and this is where you would experience quite a bit of heat loss. According to your notes, the under slab ducts run close to the outside walls. You could dig a trench around the house, exposing the foundation and install insulation board (similar to urethane or polystyrene), doubling up if necessary to get 1 1/2" or 2" insulation against the slab, using a mastic to seal the layers to the slab foundation and to each other. Water proof the top of the insulation.

If you do not have double glazed windows, you could install plastic on the inside.

Ventilating your attic in the summer will help reduce the temperature in the attic. However, I wouldn't ventilate it during the winter.

These are things you can do yourself, and would be very cost effective.

Good luck.........gs

You are right, the edge of the slab is exposed around parts of the house, particularly near the HAC system, and I checked, the supply ducts are about 12-18 inches from the edge of the the slab. I will consider adding and edge insulation. Sounds like it should have a positive affect.

I have been thinking of adding fiberglass batted insulation on top of the existing attic insulation as you suggest. The current insulation is batted fiber between the two-by-fours and as you guessed, it has settled, and thinned out significantly in some small areas.

I actually did have new siding,with form fitted insulation under it, installed a few months back along with Low-E windows all around. I'm sure this is having some affect, but this recent cold spell is the only real test of savings from it that I have so far, and we haven't seen the energy bill for that yet.

I appreciate your suggestions. Thank you for the response.

OLD F**T:

Great advice as usual.

I would only clarify that on the perimeter insulation of the slab, that the exposed portion above ground is even more important to be insulated (I'm sure you assumed that, but it wasn't clear). For aesthetic reasons if necessary, you can cover the exposed insulation with some sort of decorative or "camouflaging" facing. Also, as a minor caveat, if you live in an area with subterranean termites, take that into account when applying the insulation, by pre-treatment against them or some other means, as it could provide a sheltered, and no longer visible means of access to any wooden structure resting on the slab.

He should retain passive venting in the winter to vent moisture and prevent any condensation on the attic walls and underside of the roof. This is important, and I have seen much damage caused by people unwittingly closing off the attic vent openings to "retain" heat. This is an unheated, uninsulated area and must be vented (as opposed to actively ventilated by fan or other means which is advisable in the hot weather).

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As to how much to insulate the attic ductwork, mentioned in other posts, as much as possible! At least 8" in addition to what you have now would be my minimum, with sealing by tape or other means to prevent any direct air infiltration to the duct. You don't have to insulate the bottom of the duct if it is against the ceiling insulation and not exposed to the attic air. Often you can lay insulation bats over the ductwork and around the sides, meeting the ceiling insulation, then cover the duct insulation with good quality sheet plastic or foil backed paper, which would overlap the ceiling insulation on both sides of the duct for a foot or so. Then pour some loose insulation on top of the edges to "seal" it. The present insulation is woefully inadequate, but I wouldn't remove it. After checking for any possible air leaks and sealing them, go over it with the new.

Regards,

Greg

GREG...............You brought up an interesting point about termites.......I'm passing along a procedure used by my son-in-law during construction of his home....With a slab on grade, after he removed the forms and before backfilling, he placed a soaker hose in the bottom of the trench with the end capped, bringing the other end above grade in an inconspecious corner and capping it. Periodically he pours insecticide down the hose for even distribution along the foundation.......pretty clever, huh!......Thanks for the kind words.

g scott

G Scott,

In a (seems like) former life I was a licensed General Contractor, and for a shorter but concurrent time a Registered Pesticide Applicator (read exterminator)! At that time, the treatment of choice for Reticilurmes flavipes (the eastern subterranean termite) was soil injection of chlordane or heptaclor to create a chemical barrier around the structure and in areas of possible access from the soil to wood (stoops, chimneys etc). These pesticides after application and "drying", became oil-soluble crystals, impervious to water and would stay in place and remain effective for decades. That class of chemicals have been illegal for that use for many years now in the U.S.

I specifically remember a movie shown in a class of a wood frame house in Australia that was still standing, yet completely destroyed by subterranean termites.

I reserve the use of any pesticides on my own property for only very special situations, knowing as I do that many are essentially identical to nerve agents used in chemical warfare. But termites must be protected against and as long as your son doesn't have a well nearby or there is no danger of groundwater contamination, I think the hose is a great idea!

I also hope he installed a proper (mechanical) termite shield between the slab and wood framed exterior walls.

Greg

Something that will help are some doble glass on the roof.

It will hot the house on winter.

Cover it on summer.

I suggest you upgrade to what we call R2000. This invoves a combination of total vapor sealing of the house as well as insulation on ceiling and walls.

It is often difficult to retrofit insulation in older houses. The closed cell blue or pink solid foam is best. Foamed in place urethane also very good. Fiberglass is inferior, but cheap.

If you plan to live there for 20 years and you can save $1000/year with $5000 worth of insulation, go for it. Contractors charge $20,000 for $2000-3000 worth of insulation, so ig you are capable of the work it is well worth hile going to high R values.

If you have to pay contractors, the economics differ. Putting high R value insulation in as you build a house costs about $5000 for $3000 worth of insulation as bulk methods can be used at this stage

I will have to look into this R2000 upgrade. I did recently have new siding with form-fitted urathane insulation behind it. I was told that this insulation provides a vapor barrior.

I also had new "low-e" windows installed all around, including rear glass sliding doors. I would like to put some spray-in insulation into the top of the walls, as I assume the original has likely fallen down a little and there could be little to no inssulation in the top foot or so of the exterior walls. I have no experience with this so I don't realy know the likelyhood of my assumption being true. Also, this does seem like a lot of work, and I can't really afford a contractor at this time.

I'm not sure what doble glass is. Did you mean double glass pains? If not, I'd like to know what this doble glass is if you would explain.

I have the same issues and tried a solution that was hard to measure, then a REAL solution that is easy to measure.

Hard to measure reduction in energy bill version:

I installed attic vent all along the ridge line. You cut a two inch wide slot right down the ridge line of a pitched roof, and after the hysterical screams from your wife, and my joke of "I'm just lettin hot air out baby" and her reply of "But rain and snow will come in later you moron" . . and my reply of "Ya know . . . ya has a reeel good pint darlin . . . I should uf thunk about this ferst" (she will run inside and call her mother with the "I should have married Phil, the dentist" story AGAIN) then you go get some ridge line vent material which is 1" thick "Scotch Brite" type mesh about 8" wide and lay it over the ridge. Then you cover it with ridge line shingles but don't pound the nails home (don't crush the 1" think vent material). You can buy it preformed also as a ridge line cap. It works off the pressure differential principal that when a breeze blows over your ridge line, a pressure drop is created on the back side and cooler air is sucked in through your soffit vents and purges hot air out of your attic. Suppliers claim dramatic drops in attic temps and some shingle manufacturers will only give you their warranty with it installed. It is shown in demo tapes (biased) that it vents better than turbine vents (smoke tests showing the purging action). And for winter, the claim is that it vents moisture created from natural gas systems that freezes under your roof, therefore you have less ice up in your attic (never saw ice in my attic anyway, and while burning natural gas does produce tons of water vapor, the flue gasses go up and out, not into the house). Cooler summer / warmer winter attic temps is the claim. Don't know about that but it was worth it to see my wife's face when I 'Skill sawed' a two inch wide strip in 100 feet of her ridge caps !!!!

Measureable 75% reduction in energy version:

I put a wood stove in our living space. We don't occupy the whole house, only kitchen and family room, unless we are sleeping. Electric blankets at night, no heat, and wood stove in the living space. My landed cost for hardwood (high BTU) is $40 / cord (not including my labor, but, including chain saw, splitter, truck depreciation, gas, oil, tires, maintenace all in) and I worked out the BTU / square foot and the stove paid for itself in 1.8 years (excel spread sheet with all the above plugged in). For summer I just tell my wife "Sweat baby . . sweat !" and never turn on the AC. I open windows at different corners to get a pressure drop across the house and auto-vent it (drops a few degrees inside - but not much). Then I'll just give her a few ICE COLD BEERS which does several things: Cools her off a bit, gets her drunk so she doesn't know she is hot, and, I start to look pretty good when she is drunk (she forgets about Phil, the dentist). It is important to begin with a name brand beer first, then when the 'drunkometer' hits 3, switch to Buckhorn or some cheap stuff, further reducing your 'energy' costs.

If your evenings are appreciably cooler than your days, what works well is a large exhaust fan in or near the ceiling at the highest level, if more than one story. You open the windows furthest away from the fan to draw air through the house, and run it at night. As morning approaches, you must turn it off, and close all windows or you will have excessive dampness if you have high humidity, from the warm moist daytime air being pulled into a cool house. Typically, by the time the house temperature approaches the outdoor temperature, it is evening. This scenario works very well here on Long Island where we suffer from high humidity, and I only need to run the A/C at times when the nighttime temp is too high, and/or it is raining. I do confess however to running the A/C much more than I have to the past few years because of the high humidity and my dislike of it.

The problem appears to be the fact that your supply duct is encased in concrete, which is not a good insulator when poured in "pad form". Concrete is very porous and I'm confident that there were trapped pockets of air when it was poured.

Typically, when a house is constructed on a pad, a spilt unit system is utilized. The condenser is located outside and the evaporator/blower is located in a closet or in the attic.

If a closet is the case, then the location should be centralized within the house. The return air grill would be directly below the evaporator/blower, the supply air would be straight up into an insulated trunk that would reside in the attic, distributing to all of the insulated supply ducts that would discharge into all of the rooms.

If the evaporator/blower is in the attic, then the insulated return air duct would run to a centralized location in the house and terminate at a grill and the insulated supply trunk would do the same thing as mentioned above.

When sizing a unit for residential use, divide the square footage by 550. If we use a 2000 sq. ft dimension, we arrive at 3.6 tons. Then multiply 3.6 x 12,000 btu's and you arrive at 43,200 btu's. Your HVAC system will need to have the capacity of 43,200 btu's. Because all HVAC manufacturers have different ways of stating what a "ton" is, btu's is the number that you will want to use.

Not sure where you reside, but if the winter temps are 38 deg. F. and colder, you will want to use a gas pack split unit. Heat pumps are great if the winter temps are above 38 deg. F. But if the heat pump cannot maintain a constant temp output because the outside air is dipping into the lower 30's, then the emergency heat coils activate and your efficiency drops dramatically. Speaking of efficiency, the higher the SEER rating, the more efficient the system.

You will also want to insulate your attic heavily and if your evaporator/blower resides there, then you will want to insulate between the roof joists as well. Just be sure to use an air gap baffle between the insulation and the roof decking on every other joist.

Essentially, if your HVAC system does not meet the criteria outlined above, you will have difficulty heating on the coldest days and cooling on the hottest days. You could try to change the insulating properties of your concrete slab or modify your return line, but the inherent problem resides within the placement of the supply duct, the size of the supply duct, the location of the evaporator/blower and possibly the size and type of heating system that is being used. You did not specify the square footage of your home, what state you reside in or the type of heating system used.

Trane or York are the better units available and appear to have the higher SEER ratings, but are little more expensive than other competitors.

Good Luck!

Jeff

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Attic insulation is a important aspect against heat in homes. With the current emphasis on heat energy conservation and optimization of energy usage attic insulation has come to the forefront of aspects demanding urgent attention. Insulate it with a water heater "blanket" to help reduce costs.Proper attic insulation keeps heat in during the winter and out during. You can help reduce your impact on the environment by improving your home's energy efficiency.

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