What does 7% of total cost mean? Is the house built on a concrete slab?

My new build will be in zone 7. It can go below freezing.

I'll say!

In-floor heating provides an even heating--no cycling on and off as in forced-air systems.

the floor may not be as cool in summer without the sub-floor insulation

Yes, in summer, basements in cold climates are often so cold during the ac season that the problem is keeping the basement warm enough.

However, in-slab heating must be insulated below the coils, otherwise you're trying to heat the earth.

Radiant is awesome, but a luxury.

7% means nothing. Is it a $150, $200, $300 or $500 psf build? Neither impacts the cost of radiant heat.

My last pricing was more than conventional HVAC once it was accommodated in the foundation costs, and it didn't replace the cooling portion, so it more than doubled the HVAC costs.

@mike-home Yes, it is built on slab. I meant 7% of total construction cost.

@worthy Ooops, I meant zone 5. It will be insulated below the coil. That will make it insulated in summer from the cool temperature in ground, I would think. I was counting on summer cooling from the ground as well as A/C.

The builder wants an additional 7% to upgrade to radiant? That's a lot of money. As stated above radiant heating is a luxury item, and will likely have higher heating costs than a forced air system. You have to decide if the added comfort is worth the money.

Regardless of what heating system you get, you should insulate the slab. The slab being a few degrees cooler in the summer is not going to make much of difference in summer comfort or cost in my opinion.

The overall construction cost is low relatively speaking. My current home has wood floors except in the kitchen and bathrooms. There I have put heat mats. That works pretty well. Would that be a good compromise? I will have a furnace and forced air heating as primary source of heat. And it is in a mild climate.

The upside of radiant floor heat is that it's awesome, the downside is that if something goes wrong during/after installation or if it breaks, it could end up not worth fixing. My dad put in one on concrete under a stone floor and a line got punctured or something and was horrible/impossible? to fix and it hasn't been operable for like a decade.

I considered radiant under wood flooring (quarter sawn oak) for my kitchen to get the cast iron radiator out of the way, but it would be expensive and not as straight forward as hooking the tubes up to the radiator pipes (need mixing valves and such because of different temp requirements), and considering the bad luck my dad has had with his system, the old radiator suddenly seems less in the way.

I live in zone 5 also. I am building on a slab, it will be well insulated. The first floor will be polished concrete, but the PR and Master bath will be tiled and I have the option to do radiant heat under the tile. If I do it, it will be in the master bath only.

What kind of radiant heat are you considering? According to my builder, for the pipe kind the cost is about same regardless of the size.

You will still need an air handler and ductwork if you live somewhere that AC will also need to be installed.

I know. I will also have a furnace. That negates the benefit of radiant heat. I think I will use a heat mat to heat the floor just to take off the chill instead of radiant heat.

An electric heat mat is only practical for small limited areas like baths. It is not meant for large expanses in large rooms. It also is not very budget oriented.

A better choice would be a warmer to the feet flooring, like wood, and rugs. With the proper under slab insulation for building a slab in a cold climate.

Slab is an unusual choice for cold climate construction. Most people just do basements. It’s cheaper and gives you additional living space for very little additional money.

It's not in a cold climate. It's in zone 5 not 7. My mistake. Heat in summer is a greater problem than cold in winter. I thought slab will be good in summer.