Insulating below slab-on-grade floors

That is a common question, and a hot topic that often brings dissagreement, but we like that though! So much so that we have a page highlighting the pros and cons, check it out -

Slab on Grade or Foundation and Basement; Which is Best?

But to address your questions specifically, I've included your questions in the response to make it easier for both of us -

1. Cost - I know a slab is cheaper but having a basement that we can finish allows for a smaller footprint with less walls and roof material. Is there a big difference in cost?

We have typically found above-grade walls to be a more affordable building option, but no, it is not a huge difference. A basement will result in a much higher excavation cost to begin with, but also, concrete is a more expensive structural material compared to wood, so an above grade wall assembly can usually achieve a higher performance level for a lower cost since you can use wood as the structure. Yes, you will have a greater amount of above grade wall to build, but as mentioned, that can cost less than the same amount of below grade wall.

另一方面，也有ICF的倡导者(绝缘混凝土形式)，他们会主张使用地下室，包括从下到上的ICF墙;那些建筑商会说，成本没有太大差别。

就我个人而言，我不会基于成本而做出决定，而是基于其他一些问题，即:耐用性、生活质量和生态影响。水泥制造会排放大量的温室气体，而适合混凝土生产的沙子正成为日益稀缺的全球资源，而木材是可再生的。这就是为什么我们作为一个组织喜欢推广更可持续的选择，限制混凝土的使用是其中的很大一部分，因此我们喜欢石板。

至于耐久性——地下室的墙壁不能干燥到外部，所以在设计和建造低于等级的墙壁时必须更加谨慎。而且，地下室进水，这只是生活的一部分。我们可以采取措施，用排水系统和蓄水池泵以及电池备份系统来缓解这种情况，以防风暴期间的电力中断，但不可能预测未来很长一段时间的降水水平，只能说看起来不太好。如果你的房子是高于等级的，而不是在洪泛区，你永远不用担心它被洪水淹没。

2. Access for mechanical - I can't get my head around having to embed drains, plumbing, electrical, etc in concrete as opposed to putting it under floor. Not to mention running ducting for ERV. Is this a valid concern? What if there is a leak in the drains, how would you ever know?

More than being a valid concern is the part about wrapping your head around it, so that's all relative. I have no problem with embedding the infrastructure in the concrete but I would have a hard time wrapping my head around the idea of digging a hole in the ground to live in it when I could be living above grade. It's more a matter of what you're used to, if you go to California for example, you'd have a hard time finding a basement because they build all their houses on slabs and don't give it a second thought. And... if a drain DID have a leak and a the occasional drop made it to the ground below, no you probably would not know, nor would you probably care.

值得关注的地方是——你不能在未来改变管道，所以你需要确定你对房子的布局满意。要想让排水管漏水，你首先得把它搞砸。所以雇一个有执照的水管工，别担心。至于供水和电线，它们应该被放入导管(一个套筒)，所以如果有问题，你可以把它们拔出来，更换它们。HRV管道不应在楼板内铺设，而应仅通过墙壁和天花板铺设。

3. What about a hybrid - we don't need a full basement, what are the implications of having half of the footprint as a slab, and half basement?

混合建筑完全没问题，但它会增加成本和建筑复杂性，所以如果是我，我不会这么做，除非有一个非常好的理由，因为房屋所在的建筑地形。A hybrid would still leave you with embedding stuff in concrete as well as the durability concerns of a basement, so that sounds to me like it will ensure you are concerned out about it whichever one you choose :)

We are currently building a new demo house, on a slab,here is a video of the installif you want to have a peek. It is entirely above grade, and as I write, the house on top is being built, which will be insulated with cellulose (recycled news print).
Here are some other pages on slabs for your interest. Don’t hesitate to write back with more concerns, we love slabs and are happy to keep the discussion going.

• Best practices for insulating basements
• Choosing between a slab and a basement