If an ICF wall is thicker and square footage for property assessment is calculated using exterior dimensions wouldn’t the ICF walled home pay more in taxes? If looking at two identical home plans where all the interior rooms have precisely the same dimensions, but one home is using ICF vs another home using 2x4 exterior walls, the ICF walled home will have a larger square footage in the tax assessment calculation. Tax assessment uses exterior dimensions in the total square footage calculation. The outcome in using ICF vs 2x4 exterior walls is increased square footage which could increase the property tax rate for the ICF house. In this scenario, I have not read much regarding the cost penalty due to increase property tax paid as a result of the increased square footage. Does anyone have thoughts around this topic?

I have heard of people successfully arguing that since the taxes are on 'heated square footage', you can't measure the outside of the building; rather, the inside is what's heated. When my house is completed, I'll try to argue that point, although I'm not optimistic. How ironic that the reward for building a more energy efficient envelope is paying more taxes.

Really? You're talking about pennies. If you feel the benefits of ICF construction can be potentially offset by pennies in additional real estate taxes, you should forget about ICF and go back to building with kindling.

So, let's say the Assessor comes out and examines your 40' X 60' ICF rancher, determining that your square footage is, indeed, 38' X 58' = 2,204 instead of 59' X 39' = 2,301, a net reduction of 4%. On the other hand, while he's there he notes that ICF should actually be classified as "Premium" construction, not to mention the fine appliances and fixtures you have, so he bumps you into another category for a 20% increase..........

I’m not sure its pennies. I have two identical interior house plans where the ICF square footage was 280 square ft more. In the city I live in the cheapest going rate is around $125/sqft which equals around $35,000 more in sale price, which in my city is around another $1,200 in taxes per year.

I found an example:
The 2x4 homes total sqft= 1574 sqft
The ICF homes total sqft = 1853 sqft
Difference = 279 sqft.
Both homes have identical matching interior dimensions. Only difference is one is built using ICF vs 2x4 walls.

Tax assessment is mostly always done on exterior dimensions so the same two houses are identical inside, but the ICF will have an additional 279 sqft more than its 2x4 counter-part.

In my city, 279 sqft goes for around $35,000 more at $125/sqft. This is around another $1,200 a year in taxes or about $100/month.

I guess, a person could build a smaller ICF house with 279 sqft less inside so the exterior dimensions are smaller and match the 2x4's total sqft of 1574. But that would also mean losing 270 sqft inside the house which is not ideal.

Has anyone heard or read anything regarding this type of comparison where two identical interior plans is built with ICF & 2x4's and then comparing the exterior dimensions - keeping all the interior dimensions identical in both houses?

Posted By alruoff on 31 Dec 2013 06:27 PM
I found an example:
The 2x4 homes total sqft= 1574 sqft
The ICF homes total sqft = 1853 sqft
Difference = 279 sqft.
Both homes have identical matching interior dimensions. Only difference is one is built using ICF vs 2x4 walls.

Tax assessment is mostly always done on exterior dimensions so the same two houses are identical inside, but the ICF will have an additional 279 sqft more than its 2x4 counter-part.

In my city, 279 sqft goes for around $35,000 more at $125/sqft. This is around another $1,200 a year in taxes or about $100/month.

I guess, a person could build a smaller ICF house with 279 sqft less inside so the exterior dimensions are smaller and match the 2x4's total sqft of 1574. But that would also mean losing 270 sqft inside the house which is not ideal.

Has anyone heard or read anything regarding this type of comparison where two identical interior plans is built with ICF & 2x4's and then comparing the exterior dimensions - keeping all the interior dimensions identical in both houses?

what kind of shape are you using?  280 sq ft seems very high for a 1853 sq ft house.  for 6" cores, that equates to > 300 linear ft of wall, and that assumes that there is no 2x4 wall of offset.  my house which is ~3600 sq ft single story home including garage only has 340 linear ft of wall.

If you take a house that is 40' x 45' outside that is 1800 sq. ft.

Offset into the house by 4" and you have 1743 sq. ft.

Offset into the house 11.25" instead and you have 1644 for 99 sq. feet. So using your numbers I believe the difference in taxes might be around $35.00 per month. You will save more then that in just heat/cooling cost.

Don't know how your taxes are assessed but ours are by market value. So yes, an ICF house is worth more per square foot so we would pay more taxes.

Hi, It was the total square footage listed on the home plan's print. This was the worse case home plan that I found so far. It does have many corners so maybe that increases the linear feet since the interior has to remain constant. I found the plan looking through the web sites that sell home prints online. Thanks -

I just looked at the plans for my house, which I built in 2008. It's 2037 sq ft inside living area, 2243 sq ft outside of walls. This does not include wall finishes, either interior or exterior. Garage is additional also. That means the 11" ICF wall covers 206 sq ft. 4/11 x 206 = 75, so ICF added about 75 sq ft to the total size of the house. This is with 9 corners and tees. In my case that is something on the order of $1200/2243 x 75 = $40 per year in property tax, pretty much chump change in the grand scheme of home construction and maintenance costs.

However, keep this in mind. Most house construction, I believe, is based on outside dimensions so if you take a 2 x 4 based plan you are most likely going to shrink the interior area to stay with even foot exterior dimensions, or add significantly more to bring the ICF wall dimensions to even foot dimensions. The even foot dimensions are based on full sizes of OSB sheathing or full sizes of ICF blocks. As much as possible avoid odd dimensioned segments of ICF blocks. If you don't you'll have interesting vertical line ups of webs on which to hang drywall and siding.

I also found a great article discussing my question/concern. Maybe it will help others like me or people in the same issues discussed in the article which I pasted the link here:
http://architangent.com/2013/05/the-hidden-costs-of-icf-the-value-of-insulated-concrete-forms/

It talks about SIP vs ICF comparison in the article, but the lost space discussed in the article or increased space in my case which results in more taxes doesn't save over the energy cost savings in my case.

As far as SIP vs ICF, I haven't looked into SIP, but it looks like a good alternative and I will do more research on that beforehand.

With all due respect, its just another blog by an uninformed person. Her figures don't make sense. If she would like to post the actual floor plan we could check it out. The house would have to be greater then 3000 sq. ft. to get those numbers or some real strange shape.

If looking at the ratios of perimeter footage to square footage, outside corners reduce the area while inside corners increase the area, so you would have to have a great deal more inside corners then outside corner to significantly change the ratio.

Home plans for sale are just rough guesses at area as there are many different ways to count up the interior space. You need to do your own math.

Any house under 2000 square feet will show a difference of area for ICF to stick of less then 150 square feet. This is based on a number of cadd drawing of different shapes I just did to give you the original numbers. It is important to get all the facts right before using them to determine the cost of building.

Your 1200 per year would indicate that the taxes in your area would be 4.29 per sq. ft. so a 1800 sq. ft. house would be $7722.00 per year.

Of course taxes don't work that way. The total value of the property is multiplied by the mill rate. Up to half of the tax load might have nothing to do with square footage. Say your total taxes are 4000.00 based on a value of 400,000.00. So if you have a lot that is valued at $150,00.00 and a landscaping and services that are worth 20,000.00 and you have built a garage and some decks and porches that are worth another 30,000.00, your house square footage only accounts for 50% of the taxes. This does not even consider if you have upgrades inside the house that contribute to higher taxes.

So if you are concerned about the tax load on the extra square footage of ICF, it is probably only 10 to 15 dollars per month. Bet your cooling/heating load is a bit higher then that?

Posted By dmaceld on 31 Dec 2013 08:24 PM
I just looked at the plans for my house, which I built in 2008. It's 2037 sq ft inside living area, 2243 sq ft outside of walls. This does not include wall finishes, either interior or exterior. Garage is additional also. That means the 11" ICF wall covers 206 sq ft. 4/11 x 206 = 75, so ICF added about 75 sq ft to the total size of the house. This is with 9 corners and tees. In my case that is something on the order of $1200/2243 x 75 = $40 per year in property tax, pretty much chump change in the grand scheme of home construction and maintenance costs.

I noticed this afternoon I goofed on my numbers above. ICF added 7/11 x 206 = 131 sq ft to the total size of the house. The property tax number should be about $70 per year.

Posted By alruoff on 31 Dec 2013 04:28 AM
If an ICF wall is thicker and square footage for property assessment is calculated using exterior dimensions wouldn’t the ICF walled home pay more in taxes? If looking at two identical home plans where all the interior rooms have precisely the same dimensions, but one home is using ICF vs another home using 2x4 exterior walls, the ICF walled home will have a larger square footage in the tax assessment calculation. Tax assessment uses exterior dimensions in the total square footage calculation. The outcome in using ICF vs 2x4 exterior walls is increased square footage which could increase the property tax rate for the ICF house. In this scenario, I have not read much regarding the cost penalty due to increase property tax paid as a result of the increased square footage. Does anyone have thoughts around this topic?

Isn't tax assessment based on the appraised market value of the home, including land value? In that case the square footage is only one factor. The type of construction, the amenities inside, the lot location, etc., all come into play in determining the value. Yes, the ICF wall can add to the square footage used in the calculation, but be careful how much weight you assign to that in the overall value assessment.

Dmaceld is correct. In our location, they measure the outside walls of the completed structure. They put that into their assessment program for sure, but it has a smaller affect compared to the type of construction. Every assessment came back as "premium" construction/space, which it is - neighbour to neighbour with different construction, but all considered "premium", ended up with very similar taxes, ICF or not.