Your question doesn’t make any sense, it has an inherent logical contradiction in it.
If saving equals investment, then, BY DEFINITION, saving is productive, since investment is productive. In fact, saving would be MORE productive than consumption, since investment is more productive than consumption. When you invest your money, you are directly or indirectly purchasing or creating something that increases productivity, thereby increasing economic growth. For example, if I loan my money to a bank in the form of a certificate of deposit (CD), I am (indirectly) investing in the economy. That bank then takes that money, loans it out to a business, which then uses the funds to buy additional machinery, purchase land, build a factory, hire additional workers, etc. In other words, you are increasing economic productivity, and thereby creating economic growth.
Here’s the catch: saving does not equal investment. Saving can equal delayed consumption. For example, I might be saving money to buy a car for my personal use. That, arguably, is NOT investment. Likewise, I might take a consumer loan out. That too, is not investment. So saving is not always investment. This is why Austrians abandon the consumption/investment dichotomy and replace it with lower order/higher order goods. A lower order good is a product that takes less time to plan and build. For example, an apple is a lower order good. It didn’t require any significant planning on the part of the farmer to produce that single apple. A factory that processes apples and turns them into applesauce is a higher order good, since it took time and planning to create that factory. The applesauce, on the other hand, is a lower order good as well.
So more saving simply means that more higher order goods are being purchased, since those are the goods that need saving to be produced. For example, Robinsoe Crusoe cannot build a fishing pole unless he first saves food so he can take a day or two to build that fishing pole and not starve. Likewise, the applesauce factory needs beforehand saving to be able to sustain the planning and production process until the factory is built.
This leads us to conclude that saving is better than consumption. Without saving, we wouldn’t be able to fund any capital projects that “grow” the economy. By increasing deficits, the government is simply diverting funding away from these market-chosen capital projects and directing them toward non-market consumption projects. This hinders economic growth.