What to tackle first

[BudgetSlasher]

I've got three big projects that I want to tackle over the coming years and am doubting what order to tackle them in; the projects are as follows:

1) A ground mount 10kw solar array that self installed. All I need to do is find an electrician to make the final connections and sign off. This would wipe out all but $12 a month of our electric bill. I've estimated that this will could less than 12.5k and save about 1,200 a year. I am aware the tax credit begins to decline next year (about 600 dollars in credit less a year)
 
2) Insulate the poured concrete walls of our basement to R-20. Our basement is a walk out the stick framed walls are R-19 fiberglass bats and the poured concrete is uninsulated above grade and I do not believe there is insulation below grade either. I would but 2 inch rigid foam over the walls, build a 2x4 (24" O.C.) wall over the the foam and will it with unfaced batt insulation. I estimate it will cost me ~2.5k, but there is no good calculator for the savings, based on some of the DOE studies I have read, I will give it an estimated savings of $350 a year in heating.

3) Upgrade the insulation in the attic from R-19 to R-60 (code now would be R-49). Currently the attic has 2x6 rafters with fiberglass batts between them. If I chose to abandon any future use of the attic I could simply blow in insulation over the existing fiberglass. This could route could be handled for ~1k and would save around $200. Ideally what I would like to do is improve attic access (currently just a scuttle hole in ac closet that is a PITA to get to) and bring that attic within the conditioned space (allowing me to better control air leakage); I would do this by adding a set of stairs to the attic and moving the insulation to the underside of the 600. I estimate that would cost approximately 6k (due to increased area, and material needed to fur out the rafters, ensure continued roof venting, and keep the insulation suspended. In would also allow me to remove the rodent waste contaminated insulation in the attic.  As the attic is full height it might be a nice selling point to have it available as storage space and would bring two short runs of heating duct full within the envelope. 

So what order would you tackle these in?

[Sibley]

I'm confused - is the solar array already built, just not hooked up? If so, get that done ASAP. Always finish projects.

Attic insulation and sealing rim joists are going to be the biggest bang for the insulation buck. Be careful of diminishing returns. If you can get 80% of the benefits with 10% of the cost, do that first.

Re the attic finishing - yes, it's great to turn it into usable space. However, be careful that you do it properly so you don't cause more problems in the long term. Lack of airflow can cause serious issues.

[BudgetSlasher]

I'm confused - is the solar array already built, just not hooked up? If so, get that done ASAP. Always finish projects.

Attic insulation and sealing rim joists are going to be the biggest bang for the insulation buck. Be careful of diminishing returns. If you can get 80% of the benefits with 10% of the cost, do that first.

Re the attic finishing - yes, it's great to turn it into usable space. However, be careful that you do it properly so you don't cause more problems in the long term. Lack of airflow can cause serious issues.

Solar is not installed. I have have priced out a kit and material to do an install, cleared with local code that the install can be done by the homeowner, all that is left if to find an electrician to do the final connections and tell the utility company that it is good to go.

The rim joist (in the basement) has already been sealed and insulated.

What specifically are you referring to when you mention 80% benefit for 10% of the cost?

Also, what air flow and issues are you referring to? If I move the insulation to the underside of the roof I will maintain airflow under the roof deck. I've been in plenty of attics that have an attic that is "semi-conditioned" (brought within the insulation envelope, but has no HVAC supply or return) that have no discernable issues; they seem to be within 5-10 degrees of the conditioned spaces and have similar humidity to the conditioned spaces.

[jpdx]

I think the answer may depend largely on what climate you live in. Where are you?

[BudgetSlasher]

I think the answer may depend largely on what climate you live in. Where are you?

New England USDA Zone 5B

[lthenderson]

Personally I would tackle improvement of the house first before tackling the solar array. Of those two projects, the sealing attic leaks and insulating is the biggest bang for your buck and would add the most to the comfort of your living areas. Between insulating the current setup or switching the attic to conditioned space, I would much prefer to leave it as is unless you really need the extra storage space. It is much easier and cheaper to insulate is as it is. It is much harder to do any roofing work (say run another vent out the roof) when you have to deal with insulation as well. Having insulation on the underneath side of the roof makes it impossible to find leaks, harder to prevent ice dams (if that is an issue for you) and a few other problems. Just some things to think about.

Insulating basement walls would be low priority for me unless you spend a ton of time in your basement. Also, since cold air is heavier and stays in the basement, I would doubt there would be that much energy savings in your winter heating bill. Insulating would definitely make the basement more comfortable if you spend more time down there. Another reason I don't like insulating and finishing basement walls is because inevitably, things leak, pipes burst and it just creates more damage that must be fixed. Saying that, I have about three fourths of my basement finished. My walls are not insulated either but we don't mind it being a bit colder in the winter. Also, the one-fourth unfinished part is underneath all the pipes that supply the bathrooms and kitchens and has a floor drain so if there is a broken pipe, it won't flood the rest of the basement.

[BudgetSlasher]

Personally I would tackle improvement of the house first before tackling the solar array. Of those two projects, the sealing attic leaks and insulating is the biggest bang for your buck and would add the most to the comfort of your living areas. Between insulating the current setup or switching the attic to conditioned space, I would much prefer to leave it as is unless you really need the extra storage space. It is much easier and cheaper to insulate is as it is. It is much harder to do any roofing work (say run another vent out the roof) when you have to deal with insulation as well. Having insulation on the underneath side of the roof makes it impossible to find leaks, harder to prevent ice dams (if that is an issue for you) and a few other problems. Just some things to think about.

Insulating basement walls would be low priority for me unless you spend a ton of time in your basement. Also, since cold air is heavier and stays in the basement, I would doubt there would be that much energy savings in your winter heating bill. Insulating would definitely make the basement more comfortable if you spend more time down there. Another reason I don't like insulating and finishing basement walls is because inevitably, things leak, pipes burst and it just creates more damage that must be fixed. Saying that, I have about three fourths of my basement finished. My walls are not insulated either but we don't mind it being a bit colder in the winter. Also, the one-fourth unfinished part is underneath all the pipes that supply the bathrooms and kitchens and has a floor drain so if there is a broken pipe, it won't flood the rest of the basement.

Thanks for the input, the only reason solar is being considered at this phase is that it is something that we plan on doing at some point (we've taken steps to decrease energy use and transition logical items to electric) and the federal tax credit begins to taper at the end of the year.

As for the attic the storage space would be nice, also there is are a couple short runs of duct work that pop into the attic that I would like to bring into the conditioned envelope (I can also envision a scenario where we transition away from heating oil where having the ability to place mechanicals in the attic would be a great benefit) and no matter how hard I try at air sealing I feel that it would be a better air seal on the underside of the roof. Good point on the obscuring any future roof leaks (as an aside our 1991-era roof is likely due for replacement soon-to-this-year). As for ice dams, correct me if I am wrong, but so long as the eave vents are connected the the ridge vent (and not obstructed by the insulation) the melt that results in dams should not take place and the whole roof should be the same temperature (so there will not be a colder spot at the eave to cause freezing of melt water).

As for the basement, as I said it is a blind spot on savings, but the people I know who have done it say they see considerable savings (though that may also be associated with improved air sealing).  And then I read things like this https://web.ornl.gov/sci/buildings/docs/factSheets/basement%20Insulation%20Technology%20fact.pdf , which point to decent cost saving. Our basement has our laundry, a pool table, my brewery, parts of my workshop . . . so basically we do spend a good bit of time down there (often huddled around the wood stove).

Edit: I forget to mention the basement also contains our boiler and it's "waste heat", our heat pump water heater, and most of our forced hot air duct work (yes forces hot air with a cold boiler, not furnace).

[lthenderson]

As for ice dams, correct me if I am wrong, but so long as the eave vents are connected the the ridge vent (and not obstructed by the insulation) the melt that results in dams should not take place and the whole roof should be the same temperature (so there will not be a colder spot at the eave to cause freezing of melt water).

The question is, how are you going to put in an vent from the eave to the ridge if you are insulating that same space to turn the attic into conditioned space? There are two schools of thoughts when it comes to preventing ice dams on roofs with conditioned attics. The first school of thought is that it depends on snow loads in your area. Snow is actually pretty insulative itself with about an R-1 per inch.  It is possible for the snow to have enough insulation with depth that it will melt on the bottom side next to your shingles when the underneath side of the roof if very well insulated and has the proper air barrier installed. That melt is fine until it gets gold enough again that it freezes so you still can get freeze thaw cycles on your shingles. Their recommendation is that you only insulate the roof for a conditioned attic if you have less than certain snow loads. The other school of thought is that the venting to prevent this from happening needs to be external to your roof decking. Typically this is achieved by nailing down slats and installing metal roofing over the top with allowances to allow the air to circulate on the bottom side of that surface. This will allow a conditioned attic in places with higher snow loads.

It is a pretty complex subject but I'll throw a link to the Building Science website which does a better job of explaining. For conditioned attics, it is about 2/3s of the way down the page.

https://www.buildingscience.com/documents/insights/bsi-046-dam-ice-dam

[Sibley]

What specifically are you referring to when you mention 80% benefit for 10% of the cost?

You familiar with the bell curve? Diminishing returns? That's the concept.

Say you have a a really inefficient house, heating system, etc. You come up with a list of 50 things you can do to make it more efficient. Sit down and figure out the cost for each item on the list AND the incremental amount saved by doing that item. You'll have some items that cost $x but have savings of $xxx, and some that cost $xxx and have savings of $x and everything in between. Yes, you could do all 50 of those items, but if you do only the items with savings of $xxx, then you'll get the majority of the benefits (saving) with a much lower cost.

Essentially, would you rather spend $10k for a savings of $50k, or spend $50k for a savings of $70k. That extra $40k of cost only got you $20k of savings.

[BudgetSlasher]

As for ice dams, correct me if I am wrong, but so long as the eave vents are connected the the ridge vent (and not obstructed by the insulation) the melt that results in dams should not take place and the whole roof should be the same temperature (so there will not be a colder spot at the eave to cause freezing of melt water).

The question is, how are you going to put in an vent from the eave to the ridge if you are insulating that same space to turn the attic into conditioned space? There are two schools of thoughts when it comes to preventing ice dams on roofs with conditioned attics. The first school of thought is that it depends on snow loads in your area. Snow is actually pretty insulative itself with about an R-1 per inch.  It is possible for the snow to have enough insulation with depth that it will melt on the bottom side next to your shingles when the underneath side of the roof if very well insulated and has the proper air barrier installed. That melt is fine until it gets gold enough again that it freezes so you still can get freeze thaw cycles on your shingles. Their recommendation is that you only insulate the roof for a conditioned attic if you have less than certain snow loads. The other school of thought is that the venting to prevent this from happening needs to be external to your roof decking. Typically this is achieved by nailing down slats and installing metal roofing over the top with allowances to allow the air to circulate on the bottom side of that surface. This will allow a conditioned attic in places with higher snow loads.

It is a pretty complex subject but I'll throw a link to the Building Science website which does a better job of explaining. For conditioned attics, it is about 2/3s of the way down the page.

https://www.buildingscience.com/documents/insights/bsi-046-dam-ice-dam

I've reviewed that before and was thinking something along the line of figure 2 (with a 2 inch baffle to get clear of the insulation) online extended the baffle all the way to the ridge vent and then putting the insulation below the baffle rather than on the floor.

I just spent some time in the attic for the first time in over a year this evening and I am rethinking converting the space to semi-conditioned (in which case I may remove the insulation that is in place, air the heck out of the ceiling and re-insulate). I'm still reassessing this outcome as I would like to have storage space up there.

What specifically are you referring to when you mention 80% benefit for 10% of the cost?

You familiar with the bell curve? Diminishing returns? That's the concept.

Say you have a a really inefficient house, heating system, etc. You come up with a list of 50 things you can do to make it more efficient. Sit down and figure out the cost for each item on the list AND the incremental amount saved by doing that item. You'll have some items that cost $x but have savings of $xxx, and some that cost $xxx and have savings of $x and everything in between. Yes, you could do all 50 of those items, but if you do only the items with savings of $xxx, then you'll get the majority of the benefits (saving) with a much lower cost.

Essentially, would you rather spend $10k for a savings of $50k, or spend $50k for a savings of $70k. That extra $40k of cost only got you $20k of savings.

I am familiar with the concept.

What I am curious is where you see my proposal going past the point of diminishing returns? My plan is to bring the basement up to current code in terms of insulation (I believe code is roughly R-13) and take the attic insulation to current code (code here is R-49 to R-60).

Part of my over thinking (and potentially going out the bell curve) is eventually I would love to ditch oil as a heat source (probably when our 30 year old boiler fails); unfortunately my options here are heating oil, propane, or electric (either straight resistive, GSPH, ASPH, or some combination thereof). Doing a little extra here or there not might be the difference between one more heat pump, more geothermal loop, or a larger resistive heater (either primary or backup).

I'm still trying to nail down the all the details on solar to see if it will really pan out.

[Sibley]

I am familiar with the concept.

What I am curious is where you see my proposal going past the point of diminishing returns? My plan is to bring the basement up to current code in terms of insulation (I believe code is roughly R-13) and take the attic insulation to current code (code here is R-49 to R-60).

Part of my over thinking (and potentially going out the bell curve) is eventually I would love to ditch oil as a heat source (probably when our 30 year old boiler fails); unfortunately my options here are heating oil, propane, or electric (either straight resistive, GSPH, ASPH, or some combination thereof). Doing a little extra here or there not might be the difference between one more heat pump, more geothermal loop, or a larger resistive heater (either primary or backup).

I'm still trying to nail down the all the details on solar to see if it will really pan out.

I offered it as more of a general how to decide what to do than specific feedback on any individual item. Anytime someone's got a long list of non-mandatory projects it's a good idea to take a step back and think big picture.

Your thoughts about spending $2.5k on insulating the basement however would probably fall into this. You have no idea what the actual ROI would be. That tells me that there's a good chance that it's not necessarily worth it. That doesn't mean that nothing is needed.

I need to seal/reseal my rim joists (or whatever it's called). But I'm not going to go the full distance and insulate the cinderblock walls of the crawl space and fully encapsulate it. I can get a big benefit just by doing the rim joists, which is fully worth the expense and time of the work.

Edit: words are hard today